Python 密码学 - RSA 加密解密

本章是上一章的延续，我们逐步了解了使用 RSA 算法实现加密并对其进行了详细讨论。

用于对密文进行解密的函数如下 −

def decrypt(ciphertext, priv_key):
   cipher = PKCS1_OAEP.new(priv_key)
   return cipher.decrypt(ciphertext)

对于公钥加密或非对称密钥加密，维护两个重要的特征很重要，即身份验证(Authentication)和授权(Authorization)。

授权(Authorization)

授权是确认发送者是唯一发送消息的过程。 下面的代码解释了这一点 −

def sign(message, priv_key, hashAlg="SHA-256"):
   global hash
   hash = hashAlg
   signer = PKCS1_v1_5.new(priv_key)
   
   if (hash == "SHA-512"):
      digest = SHA512.new()
   elif (hash == "SHA-384"):
      digest = SHA384.new()
   elif (hash == "SHA-256"):
      digest = SHA256.new()
   elif (hash == "SHA-1"):
      digest = SHA.new()
   else:
      digest = MD5.new()
   digest.update(message)
   return signer.sign(digest)

身份验证(Authentication)

可以通过下面解释的验证方法进行身份验证 −

def verify(message, signature, pub_key):
   signer = PKCS1_v1_5.new(pub_key)
   if (hash == "SHA-512"):
      digest = SHA512.new()
   elif (hash == "SHA-384"):
      digest = SHA384.new()
   elif (hash == "SHA-256"):
      digest = SHA256.new()
   elif (hash == "SHA-1"):
      digest = SHA.new()
   else:
      digest = MD5.new()
   digest.update(message)
   return signer.verify(digest, signature)

数字签名连同发件人和收件人的详细信息一起被验证。 出于安全目的，这会增加更多的安全性。

RSA 加密解密

可以使用以下代码进行RSA密码解密 −

from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP
from Crypto.Signature import PKCS1_v1_5
from Crypto.Hash import SHA512, SHA384, SHA256, SHA, MD5
from Crypto import Random
from base64 import b64encode, b64decode
hash = "SHA-256"

def newkeys(keysize):
   random_generator = Random.new().read
   key = RSA.generate(keysize, random_generator)
   private, public = key, key.publickey()
   return public, private

def importKey(externKey):
   return RSA.importKey(externKey)

def getpublickey(priv_key):
   return priv_key.publickey()

def encrypt(message, pub_key):
   cipher = PKCS1_OAEP.new(pub_key)
   return cipher.encrypt(message)

def decrypt(ciphertext, priv_key):
   cipher = PKCS1_OAEP.new(priv_key)
   return cipher.decrypt(ciphertext)

def sign(message, priv_key, hashAlg = "SHA-256"):
   global hash
   hash = hashAlg
   signer = PKCS1_v1_5.new(priv_key)
   
   if (hash == "SHA-512"):
      digest = SHA512.new()
   elif (hash == "SHA-384"):
      digest = SHA384.new()
   elif (hash == "SHA-256"):
      digest = SHA256.new()
   elif (hash == "SHA-1"):
      digest = SHA.new()
   else:
      digest = MD5.new()
   digest.update(message)
   return signer.sign(digest)

def verify(message, signature, pub_key):
   signer = PKCS1_v1_5.new(pub_key)
   if (hash == "SHA-512"):
      digest = SHA512.new()
   elif (hash == "SHA-384"):
      digest = SHA384.new()
   elif (hash == "SHA-256"):
      digest = SHA256.new()
   elif (hash == "SHA-1"):
      digest = SHA.new()
   else:
      digest = MD5.new()
   digest.update(message)
   return signer.verify(digest, signature)