ElGamal algorithm of encryption algorithm

ElGamal algorithm can be used both for data encryption and digital signature, and its security depends on the problem of computing discrete logarithm on finite field. Key pair generation method. First select a prime number p, two random numbers, G and X,g, x < P, and compute y = g^x (mod p), the public key is Y, G, and P. The private key is X. G and P can be shared by a group of users. ElGamal is used for digital signatures. The signed information is M, first select a random number k, K and p-1 coprime, compute a = g^k (mod p) and then use the extended Euclidean algorithm to solve the following equation b:m = xa + KB (mod p-1) signature is (A, b). Random number k must be discarded. Verify the following: Y^a * A^B (mod p) = g^m (mod p) must also verify that 1<= a < P is satisfied. Otherwise the signature is easy to forge. ElGamal is used for encryption. The encrypted information is M, first select a random number k,k and p-1 coprime, compute a = g^k (mod p) b = y^k M (mod p) (A, B) is ciphertext, is twice times the length of the clear text. Computing M = b/a^x (mod p) on decryption ElGamal the security of the signature depends on the discrete logarithm computation on the multiplication group (IFp) *. The prime number p must be large enough and the p-1 contains at least one large prime element to resist the attack of the Pohlig & Hellman algorithm. M should generally use the hash value of the information (such as the SHA algorithm). The safety of ElGamal mainly depends on p and G, if the signature is easy to forge, it should be guaranteed that G is irreducible to the large prime element of p-1. D.bleichenbache "Generatingelgamal signatures without knowing the Secret Key" mentioned some attack methods and countermeasures. One disadvantage of ElGamal is that its ciphertext expands exponentially. The DSA (Digital Signature algorithm) algorithm of the American DSS (Digital Signature Standard) is evolved from the ElGamal algorithm. To force (0 Votes) Tempted (0 Votes) nonsense (0 Votes) Professional (0 Votes) The title party (0 Votes) passing (0 Votes) The original text: encryption algorithm ElGamal algorithm return to network security home