ECDH Encrypted Key Exchange (IronPython 2.7.8)

ecdh_eke.py

from System.IO import MemoryStream
from System.Text import Encoding
from System.Security.Cryptography import Aes, AsymmetricAlgorithm, CryptoStream, CryptoStreamMode


class DiffieHellman:
    def __init__(self):
        self.aes = Aes.Create()
        self.diffieHellman = AsymmetricAlgorithm.Create("ECDiffieHellmanCng")
        self.PublicKey = self.diffieHellman.PublicKey.ToByteArray()
        self.IV = self.aes.IV

    def Encrypt(self, publicKey, secretMessage):
        CngKey = self.diffieHellman.PublicKey.Import()

        key = CngKey.Import(publicKey, self.diffieHellman.PublicKey.BlobFormat)
        derivedKey = self.diffieHellman.DeriveKeyMaterial(key)
        #print "Derived Key: {}".format(derivedKey)
        self.aes.Key = derivedKey

        with MemoryStream() as cipherText:
            with self.aes.CreateEncryptor() as encryptor:
                with CryptoStream(cipherText, encryptor, CryptoStreamMode.Write) as cryptoStream:
                    ciphertextMessage = Encoding.UTF8.GetBytes(secretMessage)
                    cryptoStream.Write(ciphertextMessage, 0, ciphertextMessage.Length)

            return cipherText.ToArray()

    def Decrypt(self, publicKey, encryptedMessage, iv):
        CngKey = self.diffieHellman.PublicKey.Import()

        key = CngKey.Import(publicKey, self.diffieHellman.PublicKey.BlobFormat)
        derivedKey = self.diffieHellman.DeriveKeyMaterial(key)
        #print "Derived Key: {}".format(derivedKey)

        self.aes.Key = derivedKey
        self.aes.IV = iv

        with MemoryStream() as plainText:
            with self.aes.CreateDecryptor() as decryptor:
                with CryptoStream(plainText, decryptor, CryptoStreamMode.Write) as cryptoStream:
                    cryptoStream.Write(encryptedMessage, 0, encryptedMessage.Length)

            return Encoding.UTF8.GetString(plainText.ToArray())


text = "Hello World!"

bob = DiffieHellman()
alice = DiffieHellman()

secretMessage = bob.Encrypt(alice.PublicKey, text)

#print secretMessage

decryptedMessage = alice.Decrypt(bob.PublicKey, secretMessage, bob.IV)

print decryptedMessage