Cohen's cryptosystem

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Cohen's cryptosystem[1] is a public-key cryptosystem proposed in 1998 by Bram Cohen.

Key generation[edit]

In Cohen's cryptosystem, private key is a positive integer .

The algorithm uses public-keys defined as follows:

Generate random integers chosen randomly and uniformly between and . Where is some bound.

Let and generate random integers chosen randomly and uniformly between and .

Define .

Encrypting a bit[edit]

To encrypt a bit Alice randomly adds public keys and multiplies the result by either 1 (if she wishes to send a 0) or by −1 (if she wishes to send a 1) to obtain the ciphertext .

De-cryption[edit]

To de-crypt, Bob computes

It is easy to see that if then . However, if then . Hence Bob can read the bit sent by Alice on the most significant bit of h.

References[edit]

  1. ^ Bram Cohen. "Simple Public Key Encryption". Archived from the original on October 7, 2011.