Email encryption

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Email encryption is encryption and often authentication of email messages to protect the content from being read by any but the intended recipients. Email encryption has been used by journalists and regular users to protect privacy.[1]

Email encryption can rely on public-key cryptography, in which users can each publish a public key that others can use to encrypt messages to them, while keeping secret a private key they can use to decrypt such messages or to digitally encrypt and sign messages they send.

Encryption protocols[edit]

Protocols for email encryption include:

Mail sessions encryption[edit]

The STARTTLS SMTP extension is a TLS (SSL) layer on top of the SMTP connection. While it protects traffic from being sniffed during transmission, it is technically not encryption of emails because the content of messages is revealed to, and can therefore be altered by, intermediate email relays. In other words, the encryption takes place between individual SMTP relays, not between the sender and the recipient. When both relays support STARTTLS, it may be used regardless of whether the email's contents are encrypted using another protocol.

STARTTLS is also an extension of IMAP4 and POP3, see RFC 4616.[2]


The Signed and Encrypted Email Over The Internet demonstration has shown that organizations can collaborate effectively using secure email. Previous barriers to adoption were overcome, including the use of a PKI bridge to provide a scalable public key infrastructure (PKI) and the use of network security guards checking encrypted content passing in and out of corporate network boundaries to avoid encryption being used to hide malware introduction and information leakage.

Setting up and Using Email Encryption[edit]

Most full-featured email clients (like Apple Mail, Microsoft Outlook or Mozilla Thunderbird) provide native support for S/MIME secure email (digital signing and message encryption using certificates). Other encryption options include PGP and GNU Privacy Guard (GnuPG). Free and commercial software and add-ons are available as well, such as Gpg4win or PGP Desktop Email that support the OpenPGP type of encryption.[3][4]

While PGP can protect messages, it can also be hard to use in the correct way. Researchers at Carnegie Mellon University published a paper in 1999 showing that most people couldn’t figure out how to sign and encrypt messages using the current version of PGP.[5] Eight years later, another group of Carnegie Mellon researchers published a follow-up paper saying that, although a newer version of PGP made it easy to decrypt messages, most people still struggled with encrypting and signing messages, finding and verifying other people’s public encryption keys, and sharing their own keys.[6]

Because encryption can be difficult for users, security and compliance managers at companies and government agencies automate the process for employees and executives by using encryption appliances and services that automate encryption. Instead of relying on voluntary cooperation, automated encryption, based on defined policies, takes the decision and the process out of the users' hands. Emails are routed through a gateway appliance that has been configured to ensure compliance with regulatory and security policies. Emails that require it are automatically encrypted and sent.[7]

If the recipient works at an organization that uses the same encryption gateway appliance, emails are automatically decrypted, making the process transparent to the user. Recipients who are not behind an encryption gateway then need to take an extra step, either procuring the public key, or logging into an online portal to retrieve the message.[8][9]

See also[edit]


  1. ^ Lee, Micah (July 2, 2013). "Encryption Works: How to Protect Your Privacy in the Age of NSA Surveillance". Freedom of the Press Foundation. Retrieved 1 May 2014. 
  2. ^ RFC 4616, The PLAIN Simple Authentication and Security Layer (SASL) Mechanism
  3. ^ Eric Geier, PCWorld. "How to Encrypt Your Email." Apr 25, 2012. Retrieved May 28, 2014.
  4. ^ Alan Henry, Lifehacker. "How to Encrypt Your Email and Keep Your Conversations Private." Aug 14, 2013. Retrieved May 28, 2014.
  5. ^ Klint Finley, WIRED. "Google’s Revamped Gmail Could Take Encryption Mainstream." Apr 23, 2014. Retrieved June 04, 2014.
  6. ^ In Security and Usability: Designing Secure Systems that People Can Use, eds. L. Cranor and G. Simson. O'Reilly, 2005, pp. 679-702. "Why Johnny Can’t Encrypt."
  7. ^ By Luis Rivera, SC Magazine. "Protecting customer privacy through email encryption." March 11, 2014. July 18, 2014.
  8. ^ By Luis Rivera, SC Magazine. “[1].” March 11, 2014. July 22, 2014.
  9. ^ By Stan Gibson, "[2]." April 2010. July 22, 2014.

External Links[edit]

Encryption Works: How to Protect Your Privacy in the Age of NSA Surveillance