RSA 金鑰解密

本章是對上一章的延續，在上一章中，我們逐步瞭解了使用 RSA 演算法實施加密的方法，並對它進行了詳細討論。

以下是用作解密密文的功能 −

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

對於公鑰密碼或非對稱金鑰密碼，重要的是維護兩大主要特性，即認證和授權。

授權

授權是確認傳送者是唯一發送過訊息的參與者的過程。以下程式碼解釋了這一點 −

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)

認證

可以透過如下的驗證方法進行認證 −

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)

數字簽名將與傳送者和接收者的詳細資訊一起得到驗證。這為安全目的增加了更多的權重。

RSA 金鑰解密

對於 RSA 金鑰解密，你可以使用以下程式碼 −

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)