- Cohen's cryptosystem
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Cohen's cryptosystem[1] is a public-key cryptosystem proposed in 1998 by Bram Cohen.
Contents
Key generation
In Cohen's cryptosystem, private key is a positive integer p.
The algorithm uses k public-keys
defined as follows:
Generate k random integers
chosen randomly and uniformly between − B and B. Where B is some bound.
Let
and generate k random integers
chosen randomly and uniformly between 0 and A.
Define wi = (uip + vi).
Encrypting a bit
To encrypt a bit m Alice randomly adds 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
To de-crypt, Bob computes
It is easy to see that if m = 0 then 0 < h < p / 2. However, if m = 0 then p > h > p / 2. Hence Bob can read the bit sent by Alice on the most significant bit of h.
References
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