之前讲到RSA可以用来加密和数字签名，这里是RSA用作数字签名。
Python的pycrypto库实现的数字签名有一个限制，必须对哈希（hash）值进行签名，而不能直接对原文进行数字签名。好像大部分实现都有此限制。
from Crypto.PublicKey import RSA
from Crypto.Signature import PKCS1_v1_5
import Crypto.Hash.SHA512
def rsa_sign(plaintext, key, hash_algorithm=Crypto.Hash.SHA512):
"""RSA 数字签名"""
signer = PKCS1_v1_5.new(RSA.importKey(key))
#hash算法必须要pycrypto库里的hash算法，不能直接用系统hashlib库，pycrypto是封装的hashlib
hash_value = hash_algorithm.new(plaintext)
return signer.sign(hash_value)
def rsa_verify(sign, plaintext, key, hash_algorithm=Crypto.Hash.SHA512):
"""校验RSA 数字签名"""
hash_value = hash_algorithm.new(plaintext)
verifier = PKCS1_v1_5.new(RSA.importKey(key))
return verifier.verify(hash_value, sign)
if __name__ == '__main__':
private_key = '''-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----'''
public_key = '''-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQD1t3KRf4oS3sH8PbABbXL1KBYC
nGq4C/yinpfQ2j2eUmZarHuwIMT9y5ns1lpZZTktGnypvnQjF8c0Rr/cYU53DJjg
lAgVEb3el6iU+WZ7nwLub/BNYS83zpzrhDE3Qy6qTM3evsUsekBR8x6f6Usl7KpE
I/0b+EfRSpXDdvU64wIDAQAB
-----END PUBLIC KEY-----'''
message = 'RSA数字签名演示'
signature = rsa_sign(message.encode(encoding='utf-8'), private_key)
result = rsa_verify(signature, message.encode('utf-8'), public_key)
print(result)
