ElGamal算法，是一种较为常见的加密算法，它是基于1984年提出的公钥密码体制和椭圆曲线加密体系。既能用于数据加密也能用于数字签名，其安全性依赖于计算有限域上离散对数这一难题。在加密过程中，生成的密文长度是明文的两倍，且每次加密后都会在密文中生成一个随机数K。-The ElGamal algorithm is a more common encryption algorithm, which is based on the 1984 public key cryptosystem and elliptic curve cryptography system. Both digital signature can also be used for data encryption, its security relies on computational finite field discrete logarithm problem. Generated during the encryption process, the length of the ciphertext is plaintext twice, and each encryption will generate a random number K in the ciphertext.