Signal (software)

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Signal
Logo of Signal (2020–present)
Developer(s)
Initial release29 July 2014; 6 years ago (2014-07-29)[1][2]
Stable release(s) [±]
Android5.8.10 / 20 April 2021; 19 days ago (2021-04-20)[3]
iOS5.11 / 3 May 2021; 6 days ago (2021-05-03)[4]
Desktop5.0.0 / 12 April 2021; 27 days ago (2021-04-12)[5]
Preview release(s) [±]
Android5.4.12 / 3 March 2021; 2 months ago (2021-03-03)[6][7]
iOS5.6.0.14 / 2 March 2021; 2 months ago (2021-03-02)[8]
Desktop5.1.0-beta.6 Edit this on Wikidata / 6 May 2021; 3 days ago (6 May 2021)[9]
Repository Edit this at Wikidata
Operating system
TypeEncrypted voice calling, video calling and instant messaging
License
Websitesignal.org Edit this on Wikidata

Signal is a cross-platform centralized encrypted messaging service developed by the Signal Technology Foundation and Signal Messenger LLC. It uses the Internet to send one-to-one and group messages, which can include files, voice notes, images and videos.[16] It can also be used to make one-to-one and group voice and video calls,[17][18] and the Android version can optionally function as an SMS app.[19]

Signal uses standard cellular telephone numbers as identifiers and secures all communications to other Signal users with end-to-end encryption. The apps include mechanisms by which users can independently verify the identity of their contacts and the integrity of the data channel.[19][20]

Signal's software is free and open-source. Its clients are published under the GPLv3 license,[12][13][14] while the server code is published under the AGPLv3.[15] The official Android app generally uses the proprietary Google Play Services (installed on most Android devices), though it is designed to still work without them installed. Signal also has an official client app for iOS and desktop apps for Windows, MacOS and Linux.

The non-profit Signal Foundation was launched in February 2018 with initial funding of $50 million from Brian Acton.[21] As of January 2021, Signal had more than 105 million total downloads, and the app had approximately 40 million monthly active users.[22] Signal has been installed on more than 50 million Android devices.[23]

History[edit]

2010–2013: Origins[edit]

Signal is the successor of the RedPhone encrypted voice calling app and the TextSecure encrypted texting program. The beta versions of RedPhone and TextSecure were first launched in May 2010 by Whisper Systems,[24] a startup company co-founded by security researcher Moxie Marlinspike and roboticist Stuart Anderson.[44][45] Whisper Systems also produced a firewall and tools for encrypting other forms of data.[44][46] All of these were proprietary enterprise mobile security software and were only available for Android.

In November 2011, Whisper Systems announced that it had been acquired by Twitter. Neither company disclosed the financial terms of the deal.[25] The acquisition was done "primarily so that Mr. Marlinspike could help the then-startup improve its security".[47] Shortly after the acquisition, Whisper Systems' RedPhone service was made unavailable.[48] Some criticized the removal, arguing that the software was "specifically targeted [to help] people under repressive regimes" and that it left people like the Egyptians in "a dangerous position" during the events of the Egyptian revolution of 2011.[49]

Twitter released TextSecure as free and open-source software under the GPLv3 license in December 2011.[44][50][27][51] RedPhone was also released under the same license in July 2012.[52] Marlinspike later left Twitter and founded Open Whisper Systems as a collaborative Open Source project for the continued development of TextSecure and RedPhone.[1][29]

2013–2018: Open Whisper Systems[edit]

Open Whisper Systems' website was launched in January 2013.[29]

In February 2014, Open Whisper Systems introduced the second version of their TextSecure Protocol (now Signal Protocol), which added end-to-end encrypted group chat and instant messaging capabilities to TextSecure.[30] Toward the end of July 2014, they announced plans to merge the RedPhone and TextSecure applications as Signal.[53] This announcement coincided with the initial release of Signal as a RedPhone counterpart for iOS. The developers said that their next steps would be to provide TextSecure instant messaging capabilities for iOS, unify the RedPhone and TextSecure applications on Android, and launch a web client.[53] Signal was the first iOS app to enable end-to-end encrypted voice calls for free.[1][54] TextSecure compatibility was added to the iOS application in March 2015.[55][32]

Signal Android icon, 2015–2017
Signal icon, 2015–2020

From its launch in May 2010[24] until March 2015, the Android version of Signal (then called TextSecure) included support for encrypted SMS/MMS messaging.[56] From version 2.7.0 onward, the Android application only supported sending and receiving encrypted messages via the data channel.[57] Reasons for this included security flaws of SMS/MMS and problems with the key exchange.[57] Open Whisper Systems' abandonment of SMS/MMS encryption prompted some users to create a fork named Silence (initially called SMSSecure[58]) that is meant solely for the exchange of encrypted SMS and MMS messages.[59][60]

In November 2015, the TextSecure and RedPhone applications on Android were merged to become Signal for Android.[33] A month later, Open Whisper Systems announced Signal Desktop, a Chrome app that could link with a Signal mobile client.[34] At launch, the app could only be linked with the Android version of Signal.[61] On September 26, 2016, Open Whisper Systems announced that Signal Desktop could now be linked with the iOS version of Signal as well.[62] On October 31, 2017, Open Whisper Systems announced that the Chrome app was deprecated.[10] At the same time, they announced the release of a standalone desktop client (based on the Electron framework[14]) for Windows, MacOS and certain Linux distributions.[10][63]

On October 4, 2016, the American Civil Liberties Union (ACLU) and Open Whisper Systems published a series of documents revealing that OWS had received a subpoena requiring them to provide information associated with two phone numbers for a federal grand jury investigation in the first half of 2016.[64][65][66] Only one of the two phone numbers was registered on Signal, and because of how the service is designed, OWS was only able to provide "the time the user's account had been created and the last time it had connected to the service".[65][64] Along with the subpoena, OWS received a gag order requiring OWS not to tell anyone about the subpoena for one year.[64] OWS approached the ACLU, and they were able to lift part of the gag order after challenging it in court.[64] OWS said it was the first time they had received a subpoena, and that they were committed to treat "any future requests the same way".[66]

In March 2017, Open Whisper Systems transitioned Signal's calling system from RedPhone to WebRTC, also adding the ability to make video calls with the mobile apps.[36][67][17]

2018–present: Signal Technology Foundation[edit]

On 21 February 2018, Moxie Marlinspike and WhatsApp co-founder Brian Acton announced the formation of the Signal Technology Foundation, a 501(c)(3) nonprofit organization whose mission is "to support, accelerate, and broaden Signal's mission of making private communication accessible and ubiquitous".[37][21] Acton started the foundation with $50 million in funding after leaving WhatsApp's parent company Facebook in September 2017.[21] According to the announcement, Acton is the foundation's executive chairman and Marlinspike continues as the CEO of Signal Messenger.[37] As of 2020, Signal ran entirely on donations, as a nonprofit.[68]

Between November 2019 and February 2020, Signal added support for iPads, view-once images and videos, stickers, and reactions.[69] They also announced plans for a new group messaging system and an "experimental method for storing encrypted contacts in the cloud."[69]

Signal was reportedly popularized in the United States during the George Floyd protests. Heightened awareness of police monitoring led protesters to use the app to communicate. Black Lives Matter organizers had used the app "for several years".[70][68] During the first week of June, the encrypted messaging app was downloaded over five times more than it had been during the week prior to the killing of George Floyd.[70] In June 2020, Signal Foundation announced a new feature that enables users to blur faces in photos, in response to increased federal efforts to monitor protesters.[68][71]

On 7 January 2021, Signal saw a surge in new user registrations, which temporarily overwhelmed Signal's capacity to deliver account verification messages.[72] CNN and MacRumors linked the surge with a WhatsApp privacy policy change and a Signal endorsement by Elon Musk and Edward Snowden via Twitter.[72][73] International newspapers reported similar trends in the United Arab Emirates.[74] Reuters reported that more than 100,000 people had installed Signal between 7 and 8 January.[75]

Between 12 and 14 January 2021, the number of Signal installations listed on Google Play increased from over 10 million to over 50 million.[76][77][78][79] On 15 January 2021, due to the surge of new users, Signal was overwhelmed with the new traffic and was down for all users.[80][81] On the afternoon of 16 January, Signal announced via Twitter that service had been restored.[82]

Features[edit]

Signal allows users to make one-to-one and group[83] voice and video[17] calls with up to 8 people on iOS, Android, and desktop.[18] All calls are made over a Wi-Fi or data connection and (with the exception of data fees) are free of charge, including long distance and international.[54] Signal also allows users to send text messages, files,[16] voice notes, pictures, GIFs,[84] and video messages over a Wi-Fi or data connection to other Signal users on iOS, Android and a desktop app. The app also supports group messaging.

All communications between Signal users are automatically end-to-end encrypted (the encryption keys are generated and stored on the phones, not on the servers).[85] To verify that a correspondent is really the person that they claim to be, Signal users can compare key fingerprints (or scan QR codes) out-of-band.[86] The app employs a trust-on-first-use mechanism in order to notify the user if a correspondent's key changes.[86]

On Android, users can opt into making Signal the default SMS/MMS application, allowing them to send and receive unencrypted SMS messages in addition to the standard end-to-end encrypted Signal messages.[30] Users can then use the same application to communicate with contacts who do not have Signal.[30] Sending a message unencrypted is also available as an override between Signal users.[87]

TextSecure allowed the user to set a passphrase that encrypted the local message database and the user's encryption keys.[88] This did not encrypt the user's contact database or message timestamps.[88] The Signal applications on Android and iOS can be locked with the phone's pin, passphrase, or biometric authentication.[89] The user can define a "screen lock timeout" interval, providing an additional protection mechanism in case the phone is lost or stolen.[86][89]

Signal also allows users to set timers to messages.[90] After a specified time interval, the messages will be deleted from both the sender's and the receivers' devices.[90] The time interval can be between five seconds and one week long,[90] and the timer begins for each recipient once they have read their copy of the message.[91] The developers have stressed that this is meant to be "a collaborative feature for conversations where all participants want to automate minimalist data hygiene, not for situations where your contact is your adversary".[90][91]

Signal excludes users' messages from non-encrypted cloud backups by default.[92]

Signal allows users to automatically blur faces of people in photos to protect their identities.[93][94]

Signal is integrating a system that lets users send and receive payments in MOB, short for MobileCoin, a form of cryptocurrency. As of April 2021, the system is in beta and works only in the UK[95]

Limitations[edit]

Signal requires that the user provides a phone number for verification,[96] eliminating the need for user names or passwords and facilitating contact discovery (see below).[97] The number does not have to be the same as on the device's SIM card; it can also be a VoIP number[96] or a landline as long as the user can receive the verification code and have a separate device to set up the software. A number can only be registered on one mobile device at a time.[98]

This mandatory connection to a phone number (a feature Signal shares with WhatsApp, KakaoTalk, and others) has been criticized as a "major issue" for privacy-conscious users who are not comfortable with giving out their private phone number.[97] A workaround is to use a secondary phone number.[97] The ability to choose a public, changeable username instead of sharing one's phone number with everyone they message (or share a group with) is a widely-requested feature.[97][99][100]

Using phone numbers as identifiers may also create security risks that arise from the possibility of an attacker taking over a phone number.[97]

Usability[edit]

In July 2016, the Internet Society published a user study that assessed the ability of Signal users to detect and deter man-in-the-middle attacks.[20] The study concluded that 21 out of 28 participants failed to correctly compare public key fingerprints in order to verify the identity of other Signal users, and that the majority of these users still believed they had succeeded, while in reality they failed.[20] Four months later, Signal's user interface was updated to make verifying the identity of other Signal users simpler.[101]

Architecture[edit]

Encryption protocols[edit]

Signal messages are encrypted with the Signal Protocol (formerly known as the TextSecure Protocol). The protocol combines the Double Ratchet Algorithm, prekeys, and an Extended Triple Diffie–Hellman (X3DH) handshake.[102][103] It uses Curve25519, AES-256, and HMAC-SHA256 as primitives.[19] The protocol provides confidentiality, integrity, authentication, participant consistency, destination validation, forward secrecy, backward secrecy (aka future secrecy), causality preservation, message unlinkability, message repudiation, participation repudiation, and asynchronicity.[104] It does not provide anonymity preservation, and requires servers for the relaying of messages and storing of public key material.[104]

The Signal Protocol also supports end-to-end encrypted group chats. The group chat protocol is a combination of a pairwise double ratchet and multicast encryption.[104] In addition to the properties provided by the one-to-one protocol, the group chat protocol provides speaker consistency, out-of-order resilience, dropped message resilience, computational equality, trust equality, subgroup messaging, as well as contractible and expandable membership.[104]

In October 2014, researchers from Ruhr University Bochum published an analysis of the Signal Protocol.[19] Among other findings, they presented an unknown key-share attack on the protocol, but in general, they found that it was secure.[105] In October 2016, researchers from UK's University of Oxford, Queensland University of Technology in Australia, and Canada's McMaster University published a formal analysis of the protocol.[106][107] They concluded that the protocol was cryptographically sound.[106][107] In July 2017, researchers from Ruhr University Bochum found during another analysis of group messengers a purely theoretic attack against the group protocol of Signal: A user who knows the secret group ID of a group (due to having been a group member previously or stealing it from a member's device) can become a member of the group. Since the group ID cannot be guessed and such member changes are displayed to the remaining members, this attack is likely to be difficult to carry out without being detected.[108]

As of August 2018, the Signal Protocol has been implemented into WhatsApp, Facebook Messenger, Skype,[109] and Google Allo,[110] making it possible for the conversations of "more than a billion people worldwide" to be end-to-end encrypted.[111] In Google Allo, Skype and Facebook Messenger, conversations are not encrypted with the Signal Protocol by default; they only offer end-to-end encryption in an optional mode.[92][112][109][113]

Up until March 2017, Signal's voice calls were encrypted with SRTP and the ZRTP key-agreement protocol, which was developed by Phil Zimmermann.[1][114] As of March 2017, Signal's voice and video calling functionalities use the app's Signal Protocol channel for authentication instead of ZRTP.[115][36][17]

Authentication[edit]

To verify that a correspondent is really the person that they claim to be, Signal users can compare key fingerprints (or scan QR codes) out-of-band.[86] The app employs a trust on first use mechanism in order to notify the user if a correspondent's key changes.[86]

Local storage[edit]

Once the messages are received and decrypted on a user's device, they are stored locally in a SQLite database that is encrypted with SQLCipher.[116] The key to decrypt this database is also stored locally on the user's device and can be accessed if the device is unlocked.[116][117] In December 2020, Cellebrite published a blog post announcing that one of their products could now access this key and use it to "decrypt the Signal app".[116][118] Technology reporters later published articles about how Cellebrite had claimed to have the ability to "break into the Signal app" and "crack Signal's encryption".[119][120] This latter interpretation was rejected by several experts,[121] as well as representatives from Signal, who said the original post by Cellebrite had been about accessing data on "an unlocked Android phone in their physical possession" and that they "could have just opened the app to look at the messages".[122][123] Similar extraction tools also exist for iOS devices and Signal Desktop.[124][125]

Servers[edit]

Signal relies on centralized servers that are maintained by Signal Messenger. In addition to routing Signal's messages, the servers also facilitate the discovery of contacts who are also registered Signal users and the automatic exchange of users' public keys. By default, Signal's voice and video calls are peer-to-peer.[17] If the caller is not in the receiver's address book, the call is routed through a server in order to hide the users' IP addresses.[17]

Contact discovery[edit]

The servers store registered users' phone numbers, public key material and push tokens which are necessary for setting up calls and transmitting messages.[126] In order to determine which contacts are also Signal users, cryptographic hashes of the user's contact numbers are periodically transmitted to the server.[127] The server then checks to see if those match any of the SHA256 hashes of registered users and tells the client if any matches are found.[127] The hashed numbers are thereafter discarded from the server.[126] In 2014, Moxie Marlinspike wrote that it is easy to calculate a map of all possible hash inputs to hash outputs and reverse the mapping because of the limited preimage space (the set of all possible hash inputs) of phone numbers, and that a "practical privacy preserving contact discovery remains an unsolved problem."[128][127] In September 2017, Signal's developers announced that they were working on a way for the Signal client applications to "efficiently and scalably determine whether the contacts in their address book are Signal users without revealing the contacts in their address book to the Signal service."[129][130]

Metadata[edit]

All client-server communications are protected by TLS.[114][131] Signal's developers have asserted that their servers do not keep logs about who called whom and when.[132] In June 2016, Marlinspike told The Intercept that "the closest piece of information to metadata that the Signal server stores is the last time each user connected to the server, and the precision of this information is reduced to the day, rather than the hour, minute, and second".[92]

The group messaging mechanism is designed so that the servers do not have access to the membership list, group title, or group icon.[57] Instead, the creation, updating, joining, and leaving of groups is done by the clients, which deliver pairwise messages to the participants in the same way that one-to-one messages are delivered.[133][134]

Federation[edit]

Signal's server architecture was federated between December 2013 and February 2016. In December 2013, it was announced that the messaging protocol Signal uses had successfully been integrated into the Android-based open-source operating system CyanogenMod.[135][136][137] Since CyanogenMod 11.0, the client logic was contained in a system app called WhisperPush. According to Signal's developers, the Cyanogen team ran their own Signal messaging server for WhisperPush clients, which federated with the main server, so that both clients could exchange messages with each other.[137] The WhisperPush source code was available under the GPLv3 license.[138] In February 2016, the CyanogenMod team discontinued WhisperPush and recommended that its users switch to Signal.[139] In May 2016, Moxie Marlinspike wrote that federation with the CyanogenMod servers had degraded the user experience and held back development, and that their servers will probably not federate with other servers again.[140]

In May 2016, Moxie Marlinspike requested that a third-party client called LibreSignal not use the Signal service or the Signal name.[140] As a result, on 24 May 2016 the LibreSignal project posted that the project was "abandoned".[141] The functionality provided by LibreSignal was subsequently incorporated into Signal by Marlinspike.[142]

Licensing[edit]

The complete source code of the Signal clients for Android, iOS and desktop is available on GitHub under a free software license.[12][13][14] This enables interested parties to examine the code and help the developers verify that everything is behaving as expected. It also allows advanced users to compile their own copies of the applications and compare them with the versions that are distributed by Signal Messenger. In March 2016, Moxie Marlinspike wrote that, apart from some shared libraries that are not compiled with the project build due to a lack of Gradle NDK support, Signal for Android is reproducible.[143] Signal's servers are also open source.[15]

Reception[edit]

Security[edit]

In October 2014, the Electronic Frontier Foundation (EFF) included Signal in their updated surveillance self-defense guide.[144] In November 2014, Signal received a perfect score on the EFF's secure messaging scorecard;[85] it received points for having communications encrypted in transit, having communications encrypted with keys the provider doesn't have access to (end-to-end encryption), making it possible for users to independently verify their correspondents' identities, having past communications secure if the keys are stolen (forward secrecy), having the code open to independent review (open source), having the security designs well-documented, and having a recent independent security audit.[85] At the time, "ChatSecure + Orbot", Pidgin (with OTR), Silent Phone, and Telegram's optional "secret chats" also received seven out of seven points on the scorecard.[85]

Former NSA contractor Edward Snowden has endorsed Signal on multiple occasions.[34] In his keynote speech at SXSW in March 2014, he praised Signal's predecessors (TextSecure and RedPhone) for their ease of use.[145][146] In December 2014, Der Spiegel leaked slides from an internal NSA presentation dating to June 2012 in which the NSA deemed Signal's encrypted voice calling component (RedPhone) on its own as a "major threat" to its mission of accessing users' private data, and when used in conjunction with other privacy tools such as Cspace, Tor, Tails, and TrueCrypt was ranked as "catastrophic" and led to a "near-total loss/lack of insight to target communications [and] presence".[147][148]

Following the 2016 Democratic National Committee email leak, it was reported by Vanity Fair that Marc Elias (the general counsel for Hillary Clinton's presidential campaign) had instructed DNC staffers to exclusively use Signal when saying anything negative about Republican presidential nominee Donald Trump.[149][150]

In March 2017, Signal was approved by the sergeant at arms of the U.S. Senate for use by senators and their staff.[151][152]

On the 27 September 2019, Natalie Silvanovich, a security engineer working in Google's vulnerability research team at Project Zero, disclosed how a bug in the Android Signal client could let an attacker spy on a user without their knowledge.[153] The bug allowed an attacker to phone a target device, mute the call, and the call would complete - keeping the audio open but without the owner being aware of that (however they would still be aware of a ring and / or a vibration from the initial call).[154] The bug was fixed the same day that it was reported and patched in release 4.47.7 of the app for Android.[155]

In February 2020, the European Commission recommended that its staff use Signal.[156] Following the George Floyd protests, which began in May 2020, Signal was downloaded 121,000 times in the U.S. between 25 May and 4 June.[157] In July 2020, Signal became the most downloaded app in Hong Kong on both the Apple App Store and the Google Play Store after the passage of the Hong Kong national security law.[158]

As of January 2021, Signal is regarded as one of the best contact methods to securely provide tips to major news outlets such as The Washington Post,[159] The Guardian,[160] The New York Times,[161] and The Wall Street Journal.[162]

Signal received criticism from security expert Bruce Schneier, who previously praised the app, for its plans to add cryptocurrency payments through MobileCoin. Schneier stated that this would bloat the app and attract unwanted attention from the authorities.[163]

Blocking[edit]

  Countries where Signal's domain fronting is enabled by default
  Countries where Signal is blocked (March 2021)

In December 2016, Egypt blocked access to Signal.[164] In response, Signal's developers added domain fronting to their service.[165] This allows Signal users in a specific country to circumvent censorship by making it look like they are connecting to a different internet-based service.[165][166] As of March 2021, Signal's domain fronting is enabled by default in Egypt, the United Arab Emirates, Oman, Qatar, and Iran.[167]

As of January 2018, Signal was blocked in Iran.[168][169] Signal's domain fronting feature relies on the Google App Engine (GAE) service.[169][168] This does not work in Iran because Google has blocked Iranian access to GAE in order to comply with U.S. sanctions.[168][170]

In early 2018, Google App Engine made an internal change to stop domain fronting for all countries. Due to this issue, Signal made a public change to use Amazon CloudFront for domain fronting. However, AWS also announced that they would be making changes to their service to prevent domain fronting. As a result, Signal said that they would start investigating new methods/approaches.[171][172] Signal switched from AWS back to Google in April 2019.[173]

In January 2021, Iran removed the app from app stores,[174][175] and blocked Signal.[176] Signal was later blocked by China in March 2021.[177]

Audience[edit]

Use by activists[edit]

In March 2021, the United Nations recommended Myanmar residents use Signal and ProtonMail to pass and preserve evidence of human rights violations committed during the 2021 coup.[178]

Use by criminals[edit]

By design, Signal is not able to read user messages, which precludes attempts at moderation. This has been confirmed by independent audits of Signal's algorithms.[179] According to CNN, "[t]he same technology that keeps a conversation private between you and a family member also gives a safe haven to a terrorist in Syria and the person in the United States he's trying to recruit to commit an act of mass murder."[180]

In 2016, authorities in India arrested members of a suspected ISIS-affiliated terrorist cell that communicated via Signal and Telegram.[181]

The far right, right-wing militias and white nationalists, used Signal for organizing their actions, including the Unite the Right II rally in 2018.[182][183][184][185]

Developers and funding[edit]

The development of Signal and its predecessors at Open Whisper Systems was funded by a combination of consulting contracts, donations and grants.[186] The Freedom of the Press Foundation acted as Signal's fiscal sponsor.[37][187][188] Between 2013 and 2016, the project received grants from the Knight Foundation,[189] the Shuttleworth Foundation,[190] and almost $3 million from the US government–sponsored Open Technology Fund.[191] Signal is now developed by Signal Messenger LLC, a software company founded by Moxie Marlinspike and Brian Acton in 2018, which is wholly owned by a tax-exempt nonprofit corporation called the Signal Technology Foundation, also created by them in 2018. The Foundation was funded with an initial loan of $50 million from Acton, "to support, accelerate, and broaden Signal's mission of making private communication accessible and ubiquitous".[37][21][192] All of the organization's products are published as free and open-source software.

See also[edit]

References[edit]

  1. ^ a b c d e Greenberg, Andy (29 July 2014). "Your iPhone Can Finally Make Free, Encrypted Calls". Wired. Archived from the original on 18 January 2015. Retrieved 18 January 2015.
  2. ^ Marlinspike, Moxie (29 July 2014). "Free, Worldwide, Encrypted Phone Calls for iPhone". Open Whisper Systems. Archived from the original on 31 August 2017. Retrieved 16 January 2017.
  3. ^ Signal Foundation. "Signal Private Messenger - Apps on Google Play". play.google.com.
  4. ^ Signal Messenger, LLC. "‎Signal - Private Messenger on the App Store". apps.apple.com.
  5. ^ "Releases · signalapp/Signal-Desktop". github.com.
  6. ^ "Signal Private Messenger APKs". APKMirror.
  7. ^ "Releases · signalapp/Signal-Android". github.com.
  8. ^ "Releases · signalapp/Signal-iOS". github.com.
  9. ^ "Releases · signalapp/Signal-Desktop". github.com.
  10. ^ a b c d Nonnenberg, Scott (31 October 2017). "Standalone Signal Desktop". Open Whisper Systems. Archived from the original on 15 February 2020. Retrieved 31 October 2017.
  11. ^ "Installing Signal - Signal Support". Archived from the original on 23 February 2020. Retrieved 20 March 2019.
  12. ^ a b c Open Whisper Systems. "Signal-iOS". GitHub. Archived from the original on 11 November 2014. Retrieved 14 January 2015.
  13. ^ a b c Open Whisper Systems. "Signal-Android". GitHub. Archived from the original on 30 December 2015. Retrieved 5 November 2015.
  14. ^ a b c d Open Whisper Systems. "Signal-Desktop". GitHub. Archived from the original on 8 April 2016. Retrieved 7 April 2016.
  15. ^ a b c Open Whisper Systems. "Signal-Server". GitHub. Archived from the original on 28 December 2016. Retrieved 21 November 2016.
  16. ^ a b Signal [@signalapp] (1 May 2017). "Today's Signal release for Android, iOS, and Desktop includes the ability to send arbitrary file types" (Tweet). Retrieved 5 November 2018 – via Twitter.
  17. ^ a b c d e f g Mott, Nathaniel (14 March 2017). "Signal's Encrypted Video Calling For iOS, Android Leaves Beta". Tom's Hardware. Purch Group, Inc. Retrieved 14 March 2017.
  18. ^ a b c Perez, Josh (2 September 2020). "Release v1.35.1". github.com. Signal. Retrieved 3 September 2020.
  19. ^ a b c d Frosch et al. 2016
  20. ^ a b c Schröder et al. 2016
  21. ^ a b c d Greenberg, Andy (21 February 2018). "WhatsApp Co-Founder Puts $50M Into Signal To Supercharge Encrypted Messaging". Wired. Condé Nast. Archived from the original on 22 February 2018. Retrieved 21 February 2018.
  22. ^ Curry, David (26 January 2021). "Signal Revenue & Usage Statistics (2021)". Business of Apps. Archived from the original on 26 January 2021. Retrieved 28 January 2021.
  23. ^ "Signal Private Messenger - Apps on Google Play". play.google.com. 28 January 2021. Retrieved 28 January 2021.
  24. ^ a b c "Announcing the public beta". Whisper Systems. 25 May 2010. Archived from the original on 30 May 2010. Retrieved 22 January 2015.
  25. ^ a b Cheredar, Tom (28 November 2011). "Twitter acquires Android security startup Whisper Systems". VentureBeat. Archived from the original on 12 December 2011. Retrieved 21 December 2011.
  26. ^ Yadron, Danny (9 July 2015). "Moxie Marlinspike: The Coder Who Encrypted Your Texts". The Wall Street Journal. Archived from the original on 12 July 2015. Retrieved 10 July 2015.
  27. ^ a b "TextSecure is now Open Source!". Whisper Systems. 20 December 2011. Archived from the original on 6 January 2012. Retrieved 22 January 2015.
  28. ^ Yadron, Danny (10 July 2015). "What Moxie Marlinspike Did at Twitter". Digits. The Wall Street Journal. Archived from the original on 18 March 2016. Retrieved 27 September 2016.
  29. ^ a b c "A New Home". Open Whisper Systems. 21 January 2013. Archived from the original on 29 April 2013. Retrieved 1 March 2014.
  30. ^ a b c d Donohue, Brian (24 February 2014). "TextSecure Sheds SMS in Latest Version". Threatpost. Archived from the original on 15 February 2017. Retrieved 14 July 2016.
  31. ^ Open Whisper Systems (6 March 2015). "Saying goodbye to encrypted SMS/MMS". Archived from the original on 9 December 2017. Retrieved 24 March 2016.
  32. ^ a b Geuss, Megan (3 March 2015). "Now you can easily send (free!) encrypted messages between Android, iOS". Ars Technica. Archived from the original on 3 March 2015. Retrieved 3 March 2015.
  33. ^ a b Greenberg, Andy (2 November 2015). "Signal, the Snowden-Approved Crypto App, Comes to Android". Wired. Condé Nast. Archived from the original on 26 January 2018. Retrieved 19 March 2016.
  34. ^ a b c Franceschi-Bicchierai, Lorenzo (2 December 2015). "Snowden's Favorite Chat App Is Coming to Your Computer". Motherboard. Vice Media LLC. Archived from the original on 16 December 2016. Retrieved 4 December 2015.
  35. ^ Coldewey, Devin (31 October 2017). "Signal escapes the confines of the browser with a standalone desktop app". TechCrunch. Oath Tech Network. Archived from the original on 14 May 2019. Retrieved 31 October 2017.
  36. ^ a b c Marlinspike, Moxie (14 February 2017). "Video calls for Signal now in public beta". Open Whisper Systems. Archived from the original on 15 March 2017. Retrieved 15 February 2017.
  37. ^ a b c d e Marlinspike, Moxie; Acton, Brian (21 February 2018). "Signal Foundation". Signal.org. Archived from the original on 16 February 2020. Retrieved 21 February 2018.
  38. ^ Greenberg, Andy (21 February 2018). "WhatsApp Co-Founder Puts $50M Into Signal To Supercharge Encrypted Messaging". Wired. Condé Nast. Archived from the original on 22 February 2018. Retrieved 21 February 2018.
  39. ^ Lund, Joshua (27 November 2019). "Signal for iPad, and other iOS improvements". Signal.org. Signal Messenger. Archived from the original on 28 November 2019. Retrieved 1 December 2019.
  40. ^ Greenberg, Andy (14 February 2020). "Signal Is Finally Bringing Its Secure Messaging to the Masses". Wired. Condé Nast. Archived from the original on 14 February 2020. Retrieved 15 February 2020.
  41. ^ Lund, Joshua (12 August 2020). "Accept the unexpected: Message requests are now available in Signal". signal.org. Signal Messenger. Archived from the original on 11 September 2020. Retrieved 3 September 2020.
  42. ^ Lund, Joshua (13 August 2020). "A new platform is calling: Help us test one-to-one voice and video conversations on Signal Desktop". signal.org. Signal Messenger. Archived from the original on 20 August 2020. Retrieved 3 September 2020.
  43. ^ a b Porter, Jon (15 December 2020). "Signal adds support for encrypted group video calls". The Verge. Vox Media. Archived from the original on 15 December 2020. Retrieved 18 December 2020.
  44. ^ a b c Garling, Caleb (20 December 2011). "Twitter Open Sources Its Android Moxie | Wired Enterprise". Wired. Archived from the original on 22 December 2011. Retrieved 21 December 2011.
  45. ^ "Company Overview of Whisper Systems Inc". Bloomberg Businessweek. Retrieved 4 March 2014.
  46. ^ Greenberg, Andy (25 May 2010). "Android App Aims to Allow Wiretap-Proof Cell Phone Calls". Forbes. Archived from the original on 21 January 2012. Retrieved 28 February 2014.
  47. ^ Yadron, Danny (9 July 2015). "Moxie Marlinspike: The Coder Who Encrypted Your Texts". The Wall Street Journal. Archived from the original on 12 July 2015. Retrieved 10 July 2015.
  48. ^ Greenberg, Andy (28 November 2011). "Twitter Acquires Moxie Marlinspike's Encryption Startup Whisper Systems". Forbes. Archived from the original on 14 December 2011. Retrieved 21 December 2011.
  49. ^ Garling, Caleb (28 November 2011). "Twitter Buys Some Middle East Moxie | Wired Enterprise". Wired. Archived from the original on 22 December 2011. Retrieved 21 December 2011.
  50. ^ Aniszczyk, Chris (20 December 2011). "The Whispers Are True". The Twitter Developer Blog. Twitter. Archived from the original on 24 October 2014. Retrieved 22 January 2015.
  51. ^ Pachal, Pete (20 December 2011). "Twitter Takes TextSecure, Texting App for Dissidents, Open Source". Mashable. Archived from the original on 7 March 2014. Retrieved 1 March 2014.
  52. ^ "RedPhone is now Open Source!". Whisper Systems. 18 July 2012. Archived from the original on 31 July 2012. Retrieved 22 January 2015.
  53. ^ a b Mimoso, Michael (29 July 2014). "New Signal App Brings Encrypted Calling to iPhone". Threatpost. Archived from the original on 18 January 2015. Retrieved 25 January 2015.
  54. ^ a b Evans, Jon (29 July 2014). "Talk Private To Me: Free, Worldwide, Encrypted Voice Calls With Signal For iPhone". TechCrunch. AOL. Archived from the original on 4 June 2016. Retrieved 25 June 2017.
  55. ^ Lee, Micah (2 March 2015). "You Should Really Consider Installing Signal, an Encrypted Messaging App for iPhone". The Intercept. Archived from the original on 3 March 2015. Retrieved 3 March 2015.
  56. ^ Open Whisper Systems (6 March 2015). "Saying goodbye to encrypted SMS/MMS". Archived from the original on 24 August 2017. Retrieved 24 March 2016.
  57. ^ a b c Rottermanner et al. 2015, p. 3
  58. ^ BastienLQ (20 April 2016). "Change the name of SMSSecure". GitHub (pull request). SilenceIM. Archived from the original on 23 February 2020. Retrieved 27 August 2016.
  59. ^ "TextSecure-Fork bringt SMS-Verschlüsselung zurück". Heise (in German). 2 April 2015. Archived from the original on 19 November 2018. Retrieved 29 July 2015.
  60. ^ "SMSSecure: TextSecure-Abspaltung belebt SMS-Verschlüsselung wieder". Der Standard (in German). 3 April 2015. Archived from the original on 20 November 2018. Retrieved 1 August 2015.
  61. ^ Coldewey, Devin (7 April 2016). "Now's your chance to try Signal's desktop Chrome app". TechCrunch. AOL Inc. Archived from the original on 21 October 2019. Retrieved 5 May 2016.
  62. ^ Marlinspike, Moxie (26 September 2016). "Desktop support comes to Signal for iPhone". Open Whisper Systems. Archived from the original on 7 July 2017. Retrieved 26 September 2016.
  63. ^ Coldewey, Devin (31 October 2017). "Signal escapes the confines of the browser with a standalone desktop app". TechCrunch. Oath Tech Network. Archived from the original on 14 May 2019. Retrieved 31 October 2017.
  64. ^ a b c d Perlroth, Nicole; Benner, Katie (4 October 2016). "Subpoenas and Gag Orders Show Government Overreach, Tech Companies Argue". The New York Times. Archived from the original on 24 January 2020. Retrieved 4 October 2016.
  65. ^ a b Kaufman, Brett Max (4 October 2016). "New Documents Reveal Government Effort to Impose Secrecy on Encryption Company" (Blog post). American Civil Liberties Union. Archived from the original on 25 July 2017. Retrieved 4 October 2016.
  66. ^ a b "Grand jury subpoena for Signal user data, Eastern District of Virginia". Open Whisper Systems. 4 October 2016. Archived from the original on 29 August 2017. Retrieved 4 October 2016.
  67. ^ Marlinspike, Moxie (13 March 2017). "Video calls for Signal out of beta". Open Whisper Systems. Archived from the original on 15 March 2017. Retrieved 17 July 2017.
  68. ^ a b c Wiener, Anna (19 October 2020). "Taking Back Our Privacy". The New Yorker. Archived from the original on 27 October 2020. Retrieved 27 October 2020.
  69. ^ a b Greenberg, Andy (14 February 2020). "Signal Is Finally Bringing Its Secure Messaging to the Masses". Wired. Condé Nast. Archived from the original on 14 February 2020. Retrieved 15 February 2020.
  70. ^ a b Nierenberg, Amelia (12 June 2020). "Signal Downloads Are Way Up Since the Protests Began". The New York Times. Archived from the original on 25 June 2020.
  71. ^ Lyngaas, Sean (4 June 2020). "Signal aims to boost protesters' phone security at George Floyd demonstrations with face-blurring tool". CyberScoop. Archived from the original on 14 June 2020. Retrieved 14 June 2020.
  72. ^ a b Hardwick, Tim. "Encrypted Messaging App Signal Sees Surge in Popularity Following WhatsApp Privacy Policy Update". MacRumors. Archived from the original on 9 January 2021. Retrieved 9 January 2021.
  73. ^ Duffy, Clare (12 January 2021). "Why messaging app Signal is surging in popularity right now". CNN. Archived from the original on 13 January 2021. Retrieved 12 January 2021.
  74. ^ Cabral, Alvin R. "UAE WhatsApp users look for other messaging platforms over new terms". Khaleej Times. Archived from the original on 17 January 2021. Retrieved 10 January 2021.
  75. ^ "Signal, Telegram see demand spike as new WhatsApp terms stir debate". Reuters. 8 January 2021. Archived from the original on 17 January 2021. Retrieved 10 January 2021.
  76. ^ Screenshot showing 40 million downloads between january 12 and 14, 2021.
  77. ^ "Signal Private Messenger - Apps on Google Play". Google Play. 12 January 2021. Archived from the original on 12 January 2021. Retrieved 18 January 2021.
  78. ^ "Signal Private Messenger - Apps on Google Play". 14 January 2021. Archived from the original on 14 January 2021. Retrieved 18 January 2021.
  79. ^ "Signal hits 50 million installs on Play Store amid WhatsApp privacy concerns". Android Police. 14 January 2021.
  80. ^ "Signal Status". status.signal.org. Archived from the original on 15 January 2021. Retrieved 15 January 2021.
  81. ^ "WhatsApp changes: Signal messaging platform stops working as downloads surge". BBC News. 15 January 2021. Archived from the original on 16 January 2021. Retrieved 16 January 2021.
  82. ^ @SignalApp (16 January 2021). "Signal is back!" (Tweet) – via Twitter.
  83. ^ Davenport, Corbin (14 December 2020). "Signal messaging now supports encrypted group video calls". Android Police. Archived from the original on 14 December 2020. Retrieved 15 December 2020.
  84. ^ Lund, Joshua (1 November 2017). "Expanding Signal GIF search". Open Whisper Systems. Archived from the original on 23 September 2019. Retrieved 9 November 2017.
  85. ^ a b c d "Secure Messaging Scorecard. Which apps and tools actually keep your messages safe?". Electronic Frontier Foundation. 4 November 2014. Archived from the original on 28 July 2016. Retrieved 27 August 2016.
  86. ^ a b c d e Rottermanner et al. 2015, p. 5
  87. ^ "How do I send an insecure SMS?". Archived from the original on 22 June 2018. Retrieved 22 June 2018.
  88. ^ a b Rottermanner et al. 2015, p. 9
  89. ^ a b "Screen Lock". support.signal.org. Signal. n.d. Archived from the original on 15 February 2020. Retrieved 22 November 2018.
  90. ^ a b c d Greenberg, Andy (11 October 2016). "Signal, the Cypherpunk App of Choice, Adds Disappearing Messages". Wired. Condé Nast. Archived from the original on 12 October 2016. Retrieved 11 October 2016.
  91. ^ a b Marlinspike, Moxie (11 October 2016). "Disappearing messages for Signal". Open Whisper Systems. Archived from the original on 13 June 2017. Retrieved 11 October 2016.
  92. ^ a b c Lee, Micah (22 June 2016). "Battle of the Secure Messaging Apps: How Signal Beats WhatsApp". The Intercept. First Look Media. Archived from the original on 19 February 2017. Retrieved 6 September 2016.
  93. ^ O'Flaherty, Kate. "Signal Will Now Blur Protesters' Faces: Here's How It Works". Forbes. Archived from the original on 4 June 2020. Retrieved 5 June 2020.
  94. ^ Vincent, James (4 June 2020). "Signal announces new face-blurring tool for Android and iOS". The Verge. Archived from the original on 4 June 2020. Retrieved 5 June 2020.
  95. ^ Statt, Nick (6 April 2021). "Signal is testing a payments feature that lets you send cryptocurrency to friends". The Verge. Retrieved 7 April 2021.
  96. ^ a b Kolenkina, Masha (20 November 2015). "Will any phone number work? How do I get a verification number?". Open Whisper Systems. Archived from the original on 16 January 2017. Retrieved 20 December 2015.
  97. ^ a b c d e Lee, Micah (28 September 2017). "How to Use Signal Without Giving Out Your Phone Number". The Intercept. Archived from the original on 22 January 2020. Retrieved 25 February 2018.
  98. ^ "Troubleshooting multiple devices". support.signal.org. Signal Messenger LLC. Archived from the original on 20 December 2019. Retrieved 20 March 2019.
  99. ^ "Allow different kinds of identifiers for registration · Issue #1085 · signalapp/Signal-Android". GitHub. Archived from the original on 15 February 2020. Retrieved 25 February 2018.
  100. ^ "Discussion: A proposal for alternative primary identifiers". Signal Community. 24 May 2018. Archived from the original on 28 June 2020. Retrieved 26 June 2020.
  101. ^ Marlinspike, Moxie (17 November 2016). "Safety number updates". Open Whisper Systems. Archived from the original on 17 July 2017. Retrieved 17 July 2017.
  102. ^ Unger et al. 2015, p. 241
  103. ^ Marlinspike, Moxie; Perrin, Trevor. "The X3DH Key Agreement Protocol". signal.org. Archived from the original on 23 November 2020. Retrieved 24 December 2020.
  104. ^ a b c d Unger et al. 2015, p. 239
  105. ^ Pauli, Darren. "Auditors find encrypted chat client TextSecure is secure". The Register. Archived from the original on 4 November 2014. Retrieved 4 November 2014.
  106. ^ a b Brook, Chris (10 November 2016). "Signal Audit Reveals Protocol Cryptographically Sound". Threatpost. Kaspersky Lab. Archived from the original on 14 February 2017. Retrieved 11 November 2016.
  107. ^ a b Cohn-Gordon et al. 2016
  108. ^ Rösler, Paul; Mainka, Christian; Schwenk, Jörg (2017). "More is Less: On the End-to-End Security of Group Chats in Signal, WhatsApp, and Threema" (PDF). 3rd IEEE European Symposium on Security and Privacy. Archived (PDF) from the original on 19 November 2019. Retrieved 1 November 2019.
  109. ^ a b Lund, Joshua (11 January 2018). "Signal partners with Microsoft to bring end-to-end encryption to Skype". Open Whisper Systems. Archived from the original on 2 February 2020. Retrieved 17 January 2018.
  110. ^ Marlinspike, Moxie (18 May 2016). "Open Whisper Systems partners with Google on end-to-end encryption for Allo". Open Whisper Systems. Archived from the original on 22 January 2020. Retrieved 22 August 2018.
  111. ^ "Moxie Marlinspike - 40 under 40". Fortune. Time Inc. 2016. Archived from the original on 3 February 2017. Retrieved 6 October 2016.
  112. ^ Marlinspike, Moxie (8 July 2016). "Facebook Messenger deploys Signal Protocol for end to end encryption". Open Whisper Systems. Archived from the original on 1 July 2017. Retrieved 10 May 2017.
  113. ^ Gebhart, Gennie (3 October 2016). "Google's Allo Sends The Wrong Message About Encryption". Electronic Frontier Foundation. Archived from the original on 30 August 2018. Retrieved 20 August 2018.
  114. ^ a b Marlinspike, Moxie (17 July 2012). "Encryption Protocols". GitHub. Archived from the original on 5 September 2015. Retrieved 8 January 2016.
  115. ^ Greenberg, Andy (14 February 2017). "The Best Encrypted Chat App Now Does Video Calls Too". Wired. Condé Nast. Archived from the original on 15 February 2017. Retrieved 15 February 2017.
  116. ^ a b c Ganor, Alon (10 December 2020). "Cellebrite's New Solution for Decrypting the Signal App". Cellebrite. Archived from the original on 10 December 2020. Retrieved 22 December 2020.
  117. ^ Matthew D. Green [@matthew_d_green] (10 December 2020). "Someone asked me what this Cellebrite post meant, and whether it's a big deal for Signal. From what I can see it just means Cellebrite can read your texts if they have your (unlocked) phone, which, duh" (Tweet). Retrieved 22 December 2020 – via Twitter.
  118. ^ Edward Snowden [@Snowden] (15 December 2020). "No, Cellebrite cannot decrypt Signal communications. What they sell is a forensic device cops connect to insecure, unlockable phones to download a bunch of popular apps' data more easily than doing it manually. They just added Signal to that app list. That's it. There's no magic" (Tweet). Retrieved 22 December 2020 – via Twitter.
  119. ^ Benjakob, Omer (14 December 2020). "Israeli Phone-hacking Firm Claims It Can Now Break Into Encrypted Signal App". Haaretz. Archived from the original on 21 December 2020. Retrieved 22 December 2020.
  120. ^ Wakefield, Jane (22 December 2020). "Signal: Cellebrite claimed to have cracked chat app's encryption". BBC News. Archived from the original on 24 December 2020. Retrieved 22 December 2020.
  121. ^
  122. ^ Marlinspike, Moxie (23 December 2020). "No, Cellebrite cannot 'break Signal encryption.'". signal.org. Signal Messenger. Archived from the original on 24 December 2020. Retrieved 24 December 2020.
  123. ^ Signal [@signalapp] (17 December 2020). "No, Haaretz was duped. The original blog post was about accessing data on an unlocked Android phone in their physical possession. They could have just opened the app to look at the messages" (Tweet). Retrieved 22 December 2020 – via Twitter.
  124. ^ Betz, Bradford (9 February 2021). "Court documents show FBI may have tool to access private Signal messages on locked iPhones". FOXBusiness. Retrieved 14 February 2021.
  125. ^ Abrams, Lawrence (23 October 2018). "Signal Desktop Leaves Message Decryption Key in Plain Sight". BleepingComputer. Archived from the original on 27 March 2019. Retrieved 19 March 2021.
  126. ^ a b "Privacy Policy". Signal Messenger LLC. 25 May 2018. Archived from the original on 24 June 2018. Retrieved 24 June 2018.
  127. ^ a b c Moxie Marlinspike (3 January 2013). "The Difficulty Of Private Contact Discovery". Open Whisper Systems. Archived from the original on 4 March 2016. Retrieved 14 January 2016.
  128. ^ Rottermanner et al. 2015, p. 4
  129. ^ Marlinspike, Moxie (26 September 2017). "Technology preview: Private contact discovery for Signal". Open Whisper Systems. Archived from the original on 28 September 2017. Retrieved 28 September 2017.
  130. ^ Greenberg, Andy (26 September 2017). "Signal Has a Fix for Apps' Contact-Leaking Problem". Wired. Condé Nast. Archived from the original on 27 September 2017. Retrieved 28 September 2017.
  131. ^ Frosch et al. 2016, p. 7
  132. ^ Brandom, Russell (29 July 2014). "Signal brings painless encrypted calling to iOS". The Verge. Archived from the original on 3 February 2015. Retrieved 26 January 2015.
  133. ^ Moxie Marlinspike (5 May 2014). "Private Group Messaging". Open Whisper Systems. Archived from the original on 14 July 2014. Retrieved 9 July 2014.
  134. ^ Moxie Marlinspike (24 February 2014). "The New TextSecure: Privacy Beyond SMS". Open Whisper Systems. Archived from the original on 24 February 2014. Retrieved 26 February 2014.
  135. ^ Andy Greenberg (9 December 2013). "Ten Million More Android Users' Text Messages Will Soon Be Encrypted By Default". Forbes. Archived from the original on 4 March 2014. Retrieved 28 February 2014.
  136. ^ Seth Schoen (28 December 2013). "2013 in Review: Encrypting the Web Takes A Huge Leap Forward". Electronic Frontier Foundation. Archived from the original on 1 February 2014. Retrieved 1 March 2014.
  137. ^ a b Moxie Marlinspike (9 December 2013). "TextSecure, Now With 10 Million More Users". Open Whisper Systems. Archived from the original on 25 February 2014. Retrieved 28 February 2014.
  138. ^ CyanogenMod (7 January 2014). "android_external_whispersystems_WhisperPush". GitHub. Archived from the original on 28 June 2015. Retrieved 26 March 2015.
  139. ^ Sinha, Robin (20 January 2016). "CyanogenMod to Shutter WhisperPush Messaging Service on February 1". Gadgets360. NDTV. Archived from the original on 11 October 2016. Retrieved 23 January 2016.
  140. ^ a b Edge, Jake (18 May 2016). "The perils of federated protocols". LWN.net. Archived from the original on 14 September 2016. Retrieved 5 July 2016.
  141. ^ Le Bihan, Michel (24 May 2016). "README.md". GitHub. LibreSignal. Archived from the original on 27 June 2017. Retrieved 6 November 2016.
  142. ^ "Support for using Signal without Play Services · signalapp/Signal-Android@1669731". GitHub. Archived from the original on 15 February 2020. Retrieved 3 January 2020.
  143. ^ Marlinspike, Moxie (31 March 2016). "Reproducible Signal builds for Android". Open Whisper Systems. Archived from the original on 15 May 2017. Retrieved 31 March 2016.
  144. ^ "Surveillance Self-Defense. Communicating with Others". Electronic Frontier Foundation. 23 October 2014. Archived from the original on 8 November 2014. Retrieved 25 January 2015.
  145. ^ Eddy, Max (11 March 2014). "Snowden to SXSW: Here's How To Keep The NSA Out Of Your Stuff". PC Magazine: SecurityWatch. Archived from the original on 16 March 2014. Retrieved 16 March 2014.
  146. ^ "The Virtual Interview: Edward Snowden - The New Yorker Festival". YouTube. The New Yorker. 11 October 2014. Archived from the original on 9 January 2021. Retrieved 24 May 2015.
  147. ^ SPIEGEL Staff (28 December 2014). "Prying Eyes: Inside the NSA's War on Internet Security". Der Spiegel. Archived from the original on 24 January 2015. Retrieved 23 January 2015.
  148. ^ "Presentation from the SIGDEV Conference 2012 explaining which encryption protocols and techniques can be attacked and which not" (PDF). Der Spiegel. 28 December 2014. Archived (PDF) from the original on 8 October 2018. Retrieved 23 January 2015.
  149. ^ Bilton, Nick (26 August 2016). "How the Clinton Campaign Is Foiling the Kremlin". Vanity Fair. Condé Nast. Archived from the original on 29 August 2016. Retrieved 1 September 2016.
  150. ^ Blake, Andrew (27 August 2016). "Democrats warned to use encryption weeks before email leaks". The Washington Times. The Washington Times, LLC. Archived from the original on 1 September 2016. Retrieved 1 September 2016.
  151. ^ Whittaker, Zack (16 May 2017). "In encryption push, Senate staff can now use Signal for secure messaging". ZDNet. CBS Interactive. Archived from the original on 19 July 2017. Retrieved 20 July 2017.
  152. ^ Wyden, Ron (9 May 2017). "Ron Wyden letter on Signal encrypted messaging". Documentcloud. Zack Whittaker, ZDNet. Archived from the original on 6 June 2017. Retrieved 20 July 2017.
  153. ^ https://saltdna.com/news/signal%27s-messenger-eavesdropping-exploit-saltdna-cto-shares-his-views
  154. ^ https://bugs.chromium.org/p/project-zero/issues/detail?id=1943
  155. ^ https://www.forbes.com/sites/daveywinder/2019/10/05/signal-messenger-eavesdropping-exploit-confirmedwhat-you-need-to-know
  156. ^ "EU Commission to staff: Switch to Signal messaging app". Politico EU. 20 February 2020. Archived from the original on 20 February 2020. Retrieved 20 February 2020.
  157. ^ Molla, Rani (3 June 2020). "From Citizen to Signal, the most popular apps right now reflect America's protests". Vox. Archived from the original on 7 June 2020. Retrieved 7 June 2020.
  158. ^ Lee, Timothy B. (8 July 2020). "Hong Kong downloads of Signal surge as residents fear crackdown". Ars Technica. Archived from the original on 11 July 2020. Retrieved 12 July 2020.
  159. ^ "How to share documents and news tips with Washington Post journalists". Washington Post. Archived from the original on 4 June 2020. Retrieved 17 January 2021.
  160. ^ Hoyland, Luke; Fenn, Chris. "Contact the Guardian securely". The Guardian. Archived from the original on 7 January 2021. Retrieved 17 January 2021.
  161. ^ "Tips". The New York Times. 14 December 2016. ISSN 0362-4331. Archived from the original on 9 June 2020. Retrieved 17 January 2021.
  162. ^ "WSJ.com Secure Drop". The Wall Street Journal. Archived from the original on 24 July 2020. Retrieved 17 January 2021.
  163. ^ "Signal Adds Cryptocurrency Support". Schneier on Security. 7 April 2021. Retrieved 8 April 2021.
  164. ^ Cox, Joseph (19 December 2016). "Signal Claims Egypt Is Blocking Access to Encrypted Messaging App". Motherboard. Vice Media LLC. Archived from the original on 29 June 2017. Retrieved 20 July 2017.
  165. ^ a b Marlinspike, Moxie (21 December 2016). "Doodles, stickers, and censorship circumvention for Signal Android". Open Whisper Systems. Archived from the original on 28 December 2016. Retrieved 20 July 2017.
  166. ^ Greenberg, Andy (21 December 2016). "Encryption App 'Signal' Fights Censorship with a Clever Workaround". Wired. Condé Nast. Archived from the original on 11 July 2017. Retrieved 20 July 2017.
  167. ^ "SignalServiceNetworkAccess.java". GitHub. Signal Foundation. Retrieved 16 March 2021.
  168. ^ a b c Frenkel, Sheera (2 January 2018). "Iranian Authorities Block Access to Social Media Tools". The New York Times. Archived from the original on 16 January 2018. Retrieved 15 January 2018.
  169. ^ a b "Domain Fronting for Iran #7311". GitHub. 1 January 2018. Retrieved 15 January 2018.
  170. ^ Brandom, Russell (2 January 2018). "Iran blocks encrypted messaging apps amid nationwide protests". The Verge. Vox Media. Archived from the original on 22 March 2018. Retrieved 23 March 2018.
  171. ^ Marlinspike, Moxie (1 May 2018). "A letter from Amazon". signal.org. Open Whisper Systems. Archived from the original on 3 January 2019. Retrieved 10 January 2019.
  172. ^ Gallagher, Sean (2 May 2018). "Amazon blocks domain fronting, threatens to shut down Signal's account". Ars Technica. Condé Nast. Archived from the original on 24 January 2019. Retrieved 23 January 2019.
  173. ^ Parrelli, Greyson (4 April 2019). "Attempt to resolve connectivity problems for some users". GitHub. Signal Messenger LLC. Archived from the original on 17 January 2021. Retrieved 2 May 2019.
  174. ^ "حذف سیگنال از فروشگاه‌های نرم‌افزار آنلاین در ایران". BBC News فارسی (in Persian). 15 January 2021. Retrieved 17 January 2021.
  175. ^ "پیام‌رسان سیگنال به "دستور کمیته فیلترینگ" از فروشگاه‌های آنلاین در ایران حذف شد". رادیو فردا (in Persian). Radio Farda. Retrieved 17 January 2021.
  176. ^ Jones, Rhett (27 January 2021). "Signal Blocked by Iran as Encrypted Messaging App's Popularity Explodes". Gizmodo.
  177. ^ Rita, Liao (15 March 2021). "Rising encrypted app Signal is down in China". TechCrunch. Verizon Media. Retrieved 16 March 2021.
  178. ^ Nebehay, Stephanie (17 March 2021). "U.N. team seeks evidence linking Myanmar military leaders to crimes". Reuters. Retrieved 24 March 2021.
  179. ^ Cohn-Gordon et al. 2016
  180. ^ Pagliery, Jose (7 December 2015). "Obama calls on tech giants to fight ISIS". CNN. Archived from the original on 15 December 2020. Retrieved 12 January 2021.
  181. ^ Tripathi, Rahul (11 April 2016). "Dangerous Signal: This encrypted app is helping ISIS members in India to communicate". India Times. Archived from the original on 30 September 2020. Retrieved 13 January 2021. A group of terrorist suspects in India said to be inspired by Islamic State wanted to emulate US whistleblower Edward Snowden and use encrypted communication tool Signal to stay in touch, it was revealed in interrogation by the National Investigation Agency (NIA).
  182. ^ Frenkel, Sheera (11 January 2021). "Fringe Groups Splinter Online After Facebook and Twitter Bans". New York Times. Archived from the original on 12 January 2021. Retrieved 13 January 2021. In the days since rioters stormed Capitol Hill, fringe groups like armed militias, QAnon conspiracy theorists and far-right supporters of President Trump have vowed to continue their fight in hundreds of conversations on a range of internet platforms. Some of the organizers have moved to encrypted messaging apps like Telegram and Signal, which cannot be as easily monitored as social media platforms.
  183. ^ Glaser, April (11 August 2018). "How White Supremacists Planned Their Rally in D.C." Slate. Archived from the original on 24 December 2020. Retrieved 13 January 2021. This year, Kessler and his fellow white nationalist co-organizers switched much of their rally planning throughout the summer to private groups on Facebook Messenger and the encrypted texting app Signal...
  184. ^ Daly, Kye (11 January 2021). "The online far right is moving underground". Axios. Archived from the original on 12 January 2021. Retrieved 12 January 2021. Telegram and Signal are far more stable and secure and could prove more enduring homes and recruitment stations for far-right groups.
  185. ^ Glaser, April (9 October 2018). "White Supremacists Still Have a Safe Space Online". Slate. Archived from the original on 6 January 2021. Retrieved 12 January 2021. A year later, in the runup to an ultimately barely attended sequel to Unite the Right in D.C., organizers appeared to stay off the platform, opting instead to discuss logistics over Facebook Messenger and the encrypted texting app Signal.
  186. ^ O'Neill, Patrick (3 January 2017). "How Tor and Signal can maintain the fight for freedom in Trump's America". CyberScoop. Scoop News Group. Archived from the original on 17 September 2017. Retrieved 16 September 2017.
  187. ^ Timm, Trevor (8 December 2016). "Freedom of the Press Foundation's new look, and our plans to protect press freedom for 2017". Freedom of the Press Foundation. Archived from the original on 2 February 2017. Retrieved 25 January 2017.
  188. ^ "Signal". Freedom of the Press Foundation. Archived from the original on 20 March 2018. Retrieved 31 January 2018.
  189. ^ "TextSecure". Knight Foundation. Archived from the original on 9 January 2021. Retrieved 5 January 2015.
  190. ^ "Moxie Marlinspike". Shuttleworth Foundation. Archived from the original on 15 November 2016. Retrieved 14 January 2015.
  191. ^ "Open Whisper Systems". Open Technology Fund. Archived from the original on 2 March 2019. Retrieved 1 March 2019.
  192. ^ "Signal Technology Foundation". Nonprofit Explorer. Pro Publica Inc. Archived from the original on 9 January 2021. Retrieved 7 June 2019.

Bibliography[edit]

  • Cohn-Gordon, Katriel; Cremers, Cas; Dowling, Benjamin; Garratt, Luke; Stebila, Douglas (25 October 2016). "A Formal Security Analysis of the Signal Messaging Protocol" (PDF). Cryptology ePrint Archive. International Association for Cryptologic Research (IACR). Archived (PDF) from the original on 22 February 2017. Retrieved 11 December 2016.CS1 maint: ref duplicates default (link)
  • Frosch, Tilman; Mainka, Christian; Bader, Christoph; Bergsma, Florian; Schwenk, Jörg; Holz, Thorsten (March 2016). How Secure is TextSecure?. 2016 IEEE European Symposium on Security and Privacy (EuroS&P). Saarbrücken, Germany: IEEE. pp. 457–472. doi:10.1109/EuroSP.2016.41. ISBN 978-1-5090-1752-2.CS1 maint: ref duplicates default (link)
  • Rottermanner, Christoph; Kieseberg, Peter; Huber, Markus; Schmiedecker, Martin; Schrittwieser, Sebastian (December 2015). Privacy and Data Protection in Smartphone Messengers (PDF). Proceedings of the 17th International Conference on Information Integration and Web-based Applications & Services (iiWAS2015). ACM International Conference Proceedings Series. ISBN 978-1-4503-3491-4. Archived (PDF) from the original on 27 March 2016. Retrieved 18 March 2016.CS1 maint: ref duplicates default (link)
  • Schröder, Svenja; Huber, Markus; Wind, David; Rottermanner, Christoph (18 July 2016). When Signal hits the Fan: On the Usability and Security of State-of-the-Art Secure Mobile Messaging (PDF). Proceedings of the 1st European Workshop on Usable Security (EuroUSEC '16). Darmstadt, Germany: Internet Society (ISOC). ISBN 978-1-891562-45-7. Archived from the original (PDF) on 28 August 2016. Retrieved 29 August 2016.CS1 maint: ref duplicates default (link)
  • Unger, Nik; Dechand, Sergej; Bonneau, Joseph; Fahl, Sascha; Perl, Henning; Goldberg, Ian Avrum; Smith, Matthew (2015). SoK: Secure Messaging (PDF). Proceedings of the 2015 IEEE Symposium on Security and Privacy. IEEE Computer Society's Technical Committee on Security and Privacy. pp. 232–249. doi:10.1109/SP.2015.22. Archived (PDF) from the original on 4 March 2016. Retrieved 19 March 2016.CS1 maint: ref duplicates default (link)

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