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67 lines
2.2 KiB
Python
67 lines
2.2 KiB
Python
# This file is based on TLSharp
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# https://github.com/sochix/TLSharp/blob/master/TLSharp.Core/MTProto/Crypto/AES.cs
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import pyaes
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class AES:
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@staticmethod
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def decrypt_ige(cipher_text, key, iv):
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"""Decrypts the given text in 16-bytes blocks by using the given key and 32-bytes initialization vector"""
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iv1 = iv[:len(iv)//2]
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iv2 = iv[len(iv)//2:]
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aes = pyaes.AES(key)
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plain_text = [0] * len(cipher_text)
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blocks_count = len(cipher_text) // 16
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cipher_text_block = [0] * 16
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for block_index in range(blocks_count):
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for i in range(16):
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cipher_text_block[i] = cipher_text[block_index * 16 + i] ^ iv2[i]
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plain_text_block = aes.decrypt(cipher_text_block)
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for i in range(16):
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plain_text_block[i] ^= iv1[i]
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iv1 = cipher_text[block_index * 16:block_index * 16 + 16]
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iv2 = plain_text_block[0:16]
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plain_text[block_index * 16:block_index * 16 + 16] = plain_text_block[:16]
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return bytes(plain_text)
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@staticmethod
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def encrypt_ige(plain_text, key, iv):
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"""Encrypts the given text in 16-bytes blocks by using the given key and 32-bytes initialization vector"""
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# TODO: Random padding?
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if len(plain_text) % 16 != 0: # Add padding if and only if it's not evenly divisible by 16 already
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padding = bytes(16 - len(plain_text) % 16)
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plain_text += padding
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iv1 = iv[:len(iv)//2]
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iv2 = iv[len(iv)//2:]
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aes = pyaes.AES(key)
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blocks_count = len(plain_text) // 16
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cipher_text = [0] * len(plain_text)
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for block_index in range(blocks_count):
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plain_text_block = list(plain_text[block_index * 16:block_index * 16 + 16])
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for i in range(16):
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plain_text_block[i] ^= iv1[i]
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cipher_text_block = aes.encrypt(plain_text_block)
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for i in range(16):
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cipher_text_block[i] ^= iv2[i]
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iv1 = cipher_text_block[0:16]
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iv2 = plain_text[block_index * 16:block_index * 16 + 16]
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cipher_text[block_index * 16:block_index * 16 + 16] = cipher_text_block[:16]
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return bytes(cipher_text)
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