diff options
Diffstat (limited to 'lib/Crypto/PublicKey/ElGamal.py')
| -rw-r--r-- | lib/Crypto/PublicKey/ElGamal.py | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/lib/Crypto/PublicKey/ElGamal.py b/lib/Crypto/PublicKey/ElGamal.py index a9efe75..1a157ce 100644 --- a/lib/Crypto/PublicKey/ElGamal.py +++ b/lib/Crypto/PublicKey/ElGamal.py @@ -34,7 +34,7 @@ and an element *h*, it is hard to find an integer *x* such that *g^x = h*. The group is the largest multiplicative sub-group of the integers modulo *p*, with *p* prime. The signer holds a value *x* (*0<x<p-1*) as private key, and its public -key (*g*, *p*, *y* where *y=g^x mod p*) is distributed. +key (*y* where *y=g^x mod p*) is distributed. The ElGamal signature is twice as big as *p*. @@ -48,10 +48,19 @@ the element *g^{ab}* when only *g^a* and *g^b* are known, and not *a* and *b*. As before, the group is the largest multiplicative sub-group of the integers modulo *p*, with *p* prime. The receiver holds a value *a* (*0<a<p-1*) as private key, and its public key -(*g*, *p*, *b* where *b*=g^a*) is given to the sender. +(*b* where *b*=g^a*) is given to the sender. The ElGamal ciphertext is twice as big as *p*. +Domain parameters +----------------- +For both signature and encryption schemes, the values *(p,g)* are called +*domain parameters*. +They are not sensitive but must be distributed to all parties (senders and +receivers). +Different signers can share the same domain parameters, as can +different recipients of encrypted messages. + Security -------- Both DLP and CDH problem are believed to be difficult, and they have been proved @@ -294,9 +303,8 @@ class ElGamalobj(pubkey): :attention: The number *K* shall not be reused for any other operation and shall be discarded immediately. - :attention: It is strongly recommended to have M be a digest created - via a cryptographic hash, otherwise an attacker may mount an - existential forgery attack. + :attention: M must be be a cryptographic hash, otherwise an + attacker may mount an existential forgery attack. :Return: A tuple with 2 longs. """ |