def decrypt_aes_gcm(self, msg, secret):
aes = Cipher.aes_128_gcm()
g_x, iv, ciphertext, tag = msg
d_key = self.G.expon(g_x, secret).export()
d_key = sha256(d_key).digest()[:16]
msg = aes.quick_gcm_dec(d_key, iv, ciphertext, tag)
return msg
def decrypt_message(K, iv, ciphertext, tag):
""" Decrypt a cipher text under a key K
In case the decryption fails, throw an exception.
"""
## YOUR CODE HERE
aes = Cipher.aes_128_gcm()
plain = aes.quick_gcm_dec(K, iv, ciphertext, tag)
return plain.encode("utf8")
def encrypt_aes_gcm(self, msg, public_key, session):
aes = Cipher.aes_128_gcm()
iv = urandom(16)
_, aes_private_key = self.keyGenerate(session)
x = aes_private_key[1]
g_x = aes_private_key[2]
e_key = self.G.expon(public_key, x).export()
e_key = sha256(e_key).digest()[:16]
ciphertext, tag = aes.quick_gcm_enc(e_key, iv, msg)
return (g_x, iv, ciphertext, tag)
def encrypt_message(K, message):
""" Encrypt a message under a key K """
plaintext = message.encode("utf8")
## YOUR CODE HERE
aes = Cipher.aes_128_gcm()
iv = urandom(16)
ciphertext, tag = aes.quick_gcm_enc(K, iv, plaintext)
return (iv, ciphertext, tag)
def decrypt_message(K, iv, ciphertext, tag):
""" Decrypt a cipher text under a key K
In case the decryption fails, throw an exception.
"""
## YOUR CODE HERE
aes = Cipher.aes_128_gcm() #Intialise Advanced encryption standart
plain = aes.quick_gcm_dec(
K, iv, ciphertext, tag
) # produce the plaintext using decryption function given using the arguments of the function
return plain.encode("utf8")
def encrypt_message(K, message):
""" Encrypt a message under a key K """
plaintext = message.encode("utf8")
aes = Cipher.aes_128_gcm() ## intialise aes gcm cipher
iv = urandom(16) ## Generate random IV of length 16
ciphertext, tag = aes.quick_gcm_enc(
K, iv, plaintext
) ## produce cipher and tag using the encryption function provided
## YOUR CODE HERE
return (iv, ciphertext, tag)
def decrypt_message(K, iv, ciphertext, tag):
""" Decrypt a cipher text under a key K
In case the decryption fails, throw an exception.
"""
## YOUR CODE HERE
aes = Cipher.aes_128_gcm()
decrypter = aes.dec(K, iv)
plain = decrypter.update(ciphertext)
decrypter.set_tag(tag)
decrypter.finalize()
return plain.encode("utf8")
def encrypt_message(K, message):
""" Encrypt a message under a key K """
plaintext = message.encode("utf8")
## YOUR CODE HERE
key_length = len(K)
iv = urandom(key_length)
aes = Cipher.aes_128_gcm()
encrypter = aes.enc(K, iv)
ciphertext = encrypter.update(plaintext)
encrypter.finalize()
tag = encrypter.get_tag(key_length)
return (iv, ciphertext, tag)
def test_fails():
G1, private1, public1 = dh_get_key()
msg = u"Test" * 1000
ciphertext=dh_encrypt(public1,msg)
iv=ciphertext[0]#get IV from dh_encrypt()
tag=ciphertext[2]#tag
pubA=ciphertext[3]#Alice's public key
#derive shared secret by doing qA * dB
shared=pubA.pt_mul(private1)
hashedKey=sha256(shared.export()).digest()
print "shared in fail is", shared
mess=msg.encode("utf8")
aes = Cipher.aes_128_gcm() # Initialize AES cipher
enc = aes.enc(hashedKey[:16], iv) # Get an encryption CipherOperation
ciphertext2 = enc.update(mess) # Include some plaintext
nothing = enc.finalize() # Finalize
tag2 = enc.get_tag(16) # Get the AES-GCM tag
if tag==tag2:#only attempt to decrypt if tag is valid !
assert dh_decrypt(private1,ciphertext)==mess
else:
assert False
def test_fails():
G1, private1, public1 = dh_get_key()
msg = u"Test" * 1000
ciphertext = dh_encrypt(public1, msg)
iv = ciphertext[0] #get IV from dh_encrypt()
tag = ciphertext[2] #tag
pubA = ciphertext[3] #Alice's public key
#derive shared secret by doing qA * dB
shared = pubA.pt_mul(private1)
hashedKey = sha256(shared.export()).digest()
print "shared in fail is", shared
mess = msg.encode("utf8")
aes = Cipher.aes_128_gcm() # Initialize AES cipher
enc = aes.enc(hashedKey[:16], iv) # Get an encryption CipherOperation
ciphertext2 = enc.update(mess) # Include some plaintext
nothing = enc.finalize() # Finalize
tag2 = enc.get_tag(16) # Get the AES-GCM tag
if tag == tag2: #only attempt to decrypt if tag is valid !
assert dh_decrypt(private1, ciphertext) == mess
else:
assert False
