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POPython equivalent of PHP Mcrypt
 

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    <p>I wrote the following DES encryption scheme in PHP . It uses a static Initialization Vector to make sure the output and input is one to one mapped </p> <p>PHP code :</p> <pre><code>function encrypt($plaintext, $key) { # use an explicit encoding for the plain text $plaintext_utf8 = utf8_encode($plaintext); # create a random IV to use with CBC encoding # $iv_size = mcrypt_get_iv_size(MCRYPT_DES, MCRYPT_MODE_CBC); # $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND); # defining a constant IV to use with CBC encoding $iv = "kritanj "; # creates the DES cipher text $ciphertext = mcrypt_encrypt(MCRYPT_DES, $key, $plaintext_utf8, MCRYPT_MODE_CBC, $iv); # prepend the IV for it to be available for decryption $ciphertext = $iv . $ciphertext; # encode the resulting cipher text so it can be represented by a string $ciphertext_base64 = base64_encode($ciphertext); return $ciphertext_base64; } function decrypt($ciphertext_base64, $key) { $ciphertext_dec = base64_decode($ciphertext_base64); # retrieves the IV, iv_size should be created using mcrypt_get_iv_size() # $iv_size = mcrypt_get_iv_size(MCRYPT_DES, MCRYPT_MODE_CBC); # $iv = substr($ciphertext_dec, 0, $iv_size); $iv = "kritanj "; # retrieves the cipher text (everything except the $iv_size in the front) $ciphertext_dec = substr($ciphertext_dec, $iv_size); # decrypting the DES cipher text $plaintext_utf8_dec = mcrypt_decrypt(MCRYPT_DES, $key, $ciphertext_dec, MCRYPT_MODE_CBC, $iv); return $plaintext_utf8_dec; } $plaintext = "The secret message is : " ; $key = "7chrkey" ; $ciphertext = encrypt($plaintext, $key); echo "Encrypted: ".$ciphertext ."&lt;br&gt;"; $plaintext1 = decrypt($ciphertext, $key); echo "Decrypted: ".$plaintext1 ; </code></pre> <p>Output :</p> <pre><code>Encrypted: a3JpdGFuaiB3DY63WHnE9led43FyFe53HlhUEr+vVJg= Decrypted: The secret message is : </code></pre> <p>Now I tried to write a equivalent code in python Here is what I managed</p> <p>Python code:</p> <pre><code>import binascii def conv_sevnCharKey_to_64bit_DESkey(key): st = bin(int(binascii.hexlify(key), 16)) st = st[2:] des_key = '' for i in xrange(8) : parity = 0 sevnBits = st[i*7:i*7+7] for c in sevnBits : if c in '1' : parity += 1 if parity % 2 == 0 : eigthBytes = sevnBits + '1' else : eigthBytes = sevnBits + '0' des_key += eigthBytes n = int('0b'+des_key, 2) DESkey = binascii.unhexlify('%x' % n) return DESkey from pyDes import * plaintext = "The secret message is : " iv = 'kritanj ' key = conv_sevnCharKey_to_64bit_DESkey('7chrkey') plaintext_utf8 = plaintext.encode('utf-8') # iniltalizing DES in cbc mode k = des(key, CBC, iv) # encrypting ciphertext = k.encrypt(plaintext_utf8) # prepending the IV ciphertext = iv + ciphertext; # encoding to base64 ciphertext_base64 = ciphertext.encode('base64','strict') print "Encrypted: ", ciphertext_base64 # decoding base64 ciphertext= ciphertext_base64.decode('base64','strict') # striping the IV and decrypting plaintext_utf8 = k.decrypt(ciphertext[8:]) # decoding utf-8 (if nessacary) plaintext1 = plaint`ext_utf8.decode('utf-8') print "Decrypted: ", plaintext1 assert plaintext1== plaintext </code></pre> <p>Output:</p> <pre><code>Encrypted: a3JpdGFuaiD+sGHb2GfZSXDac1r6mH+JDx7535yxL9k= Decrypted: The secret message is : </code></pre> <p>Why are the ciphertexts different? And is there a way to make sure they are identical ?</p> <p>[I want to make a 'meet in the middle' attack on a text encrypted under a double DES encryption using the above php code . But since I cant recreate the encryption I cant implement the attack]</p>
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