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Cleanup
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Mark Qvist
parent
62ecc0549d
commit
4ae0f28aa0
1 changed files with 11 additions and 222 deletions
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@ -1,17 +1,17 @@
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# MIT License
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#
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# Copyright (c) 2024 BoppreH
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in all
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# copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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@ -58,25 +58,21 @@ inv_s_box = (
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0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26, 0xE1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0C, 0x7D,
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)
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def sub_bytes(s):
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for i in range(4):
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for j in range(4):
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s[i][j] = s_box[s[i][j]]
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def inv_sub_bytes(s):
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for i in range(4):
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for j in range(4):
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s[i][j] = inv_s_box[s[i][j]]
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def shift_rows(s):
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s[0][1], s[1][1], s[2][1], s[3][1] = s[1][1], s[2][1], s[3][1], s[0][1]
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s[0][2], s[1][2], s[2][2], s[3][2] = s[2][2], s[3][2], s[0][2], s[1][2]
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s[0][3], s[1][3], s[2][3], s[3][3] = s[3][3], s[0][3], s[1][3], s[2][3]
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def inv_shift_rows(s):
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s[0][1], s[1][1], s[2][1], s[3][1] = s[3][1], s[0][1], s[1][1], s[2][1]
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s[0][2], s[1][2], s[2][2], s[3][2] = s[2][2], s[3][2], s[0][2], s[1][2]
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@ -87,11 +83,8 @@ def add_round_key(s, k):
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for j in range(4):
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s[i][j] ^= k[i][j]
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# learned from https://web.archive.org/web/20100626212235/http://cs.ucsb.edu/~koc/cs178/projects/JT/aes.c
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xtime = lambda a: (((a << 1) ^ 0x1B) & 0xFF) if (a & 0x80) else (a << 1)
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def mix_single_column(a):
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# see Sec 4.1.2 in The Design of Rijndael
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t = a[0] ^ a[1] ^ a[2] ^ a[3]
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@ -101,12 +94,10 @@ def mix_single_column(a):
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a[2] ^= t ^ xtime(a[2] ^ a[3])
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a[3] ^= t ^ xtime(a[3] ^ u)
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def mix_columns(s):
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for i in range(4):
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mix_single_column(s[i])
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def inv_mix_columns(s):
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# see Sec 4.1.3 in The Design of Rijndael
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for i in range(4):
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@ -119,7 +110,6 @@ def inv_mix_columns(s):
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mix_columns(s)
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r_con = (
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0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40,
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0x80, 0x1B, 0x36, 0x6C, 0xD8, 0xAB, 0x4D, 0x9A,
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@ -128,20 +118,11 @@ r_con = (
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)
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def bytes2matrix(text):
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""" Converts a 16-byte array into a 4x4 matrix. """
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return [list(text[i:i+4]) for i in range(0, len(text), 4)]
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def matrix2bytes(matrix):
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""" Converts a 4x4 matrix into a 16-byte array. """
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return bytes(sum(matrix, []))
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def xor_bytes(a, b):
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""" Returns a new byte array with the elements xor'ed. """
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return bytes(i^j for i, j in zip(a, b))
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def bytes2matrix(text): return [list(text[i:i+4]) for i in range(0, len(text), 4)]
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def matrix2bytes(matrix): return bytes(sum(matrix, []))
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def xor_bytes(a, b): return bytes(i^j for i, j in zip(a, b))
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def inc_bytes(a):
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""" Returns a new byte array with the value increment by 1 """
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out = list(a)
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for i in reversed(range(len(out))):
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if out[i] == 0xFF:
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@ -151,52 +132,18 @@ def inc_bytes(a):
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break
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return bytes(out)
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def pad(plaintext):
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"""
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Pads the given plaintext with PKCS#7 padding to a multiple of 16 bytes.
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Note that if the plaintext size is a multiple of 16,
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a whole block will be added.
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"""
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padding_len = 16 - (len(plaintext) % 16)
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padding = bytes([padding_len] * padding_len)
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return plaintext + padding
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def unpad(plaintext):
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"""
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Removes a PKCS#7 padding, returning the unpadded text and ensuring the
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padding was correct.
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"""
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padding_len = plaintext[-1]
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assert padding_len > 0
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message, padding = plaintext[:-padding_len], plaintext[-padding_len:]
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assert all(p == padding_len for p in padding)
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return message
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def split_blocks(message, block_size=16, require_padding=True):
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assert len(message) % block_size == 0 or not require_padding
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return [message[i:i+16] for i in range(0, len(message), block_size)]
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assert len(message) % block_size == 0 or not require_padding
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return [message[i:i+16] for i in range(0, len(message), block_size)]
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class AES256:
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"""
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Class for AES-128 encryption with CBC mode and PKCS#7.
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This is a raw implementation of AES, without key stretching or IV
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management. Unless you need that, please use `encrypt` and `decrypt`.
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"""
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rounds_by_key_size = {32: 14}
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def __init__(self, master_key):
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"""
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Initializes the object with a given key.
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"""
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assert len(master_key) in AES256.rounds_by_key_size
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self.n_rounds = AES256.rounds_by_key_size[len(master_key)]
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self._key_matrices = self._expand_key(master_key)
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def _expand_key(self, master_key):
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"""
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Expands and returns a list of key matrices for the given master_key.
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"""
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# Initialize round keys with raw key material.
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key_columns = bytes2matrix(master_key)
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iteration_size = len(master_key) // 4
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@ -228,9 +175,6 @@ class AES256:
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return [key_columns[4*i : 4*(i+1)] for i in range(len(key_columns) // 4)]
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def encrypt_block(self, plaintext):
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"""
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Encrypts a single block of 16 byte long plaintext.
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"""
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assert len(plaintext) == 16
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plain_state = bytes2matrix(plaintext)
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@ -250,9 +194,6 @@ class AES256:
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return matrix2bytes(plain_state)
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def decrypt_block(self, ciphertext):
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"""
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Decrypts a single block of 16 byte long ciphertext.
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"""
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assert len(ciphertext) == 16
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cipher_state = bytes2matrix(ciphertext)
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@ -272,18 +213,10 @@ class AES256:
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return matrix2bytes(cipher_state)
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def encrypt_cbc(self, plaintext, iv):
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"""
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Encrypts `plaintext` using CBC mode and PKCS#7 padding, with the given
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initialization vector (iv).
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"""
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assert len(iv) == 16
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plaintext = pad(plaintext)
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if len(iv) != 16: raise ValueError(f"Invalid IV length: {len(iv)}")
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blocks = []
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previous = iv
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for plaintext_block in split_blocks(plaintext):
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# CBC mode encrypt: encrypt(plaintext_block XOR previous)
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block = self.encrypt_block(xor_bytes(plaintext_block, previous))
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blocks.append(block)
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previous = block
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@ -291,157 +224,13 @@ class AES256:
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return b''.join(blocks)
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def decrypt_cbc(self, ciphertext, iv):
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"""
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Decrypts `ciphertext` using CBC mode and PKCS#7 padding, with the given
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initialization vector (iv).
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"""
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assert len(iv) == 16
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if len(iv) != 16: raise ValueError(f"Invalid IV length: {len(iv)}")
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blocks = []
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previous = iv
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for ciphertext_block in split_blocks(ciphertext):
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# CBC mode decrypt: previous XOR decrypt(ciphertext)
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blocks.append(xor_bytes(previous, self.decrypt_block(ciphertext_block)))
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previous = ciphertext_block
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return unpad(b''.join(blocks))
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def encrypt_pcbc(self, plaintext, iv):
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"""
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Encrypts `plaintext` using PCBC mode and PKCS#7 padding, with the given
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initialization vector (iv).
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"""
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assert len(iv) == 16
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plaintext = pad(plaintext)
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blocks = []
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prev_ciphertext = iv
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prev_plaintext = bytes(16)
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for plaintext_block in split_blocks(plaintext):
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# PCBC mode encrypt: encrypt(plaintext_block XOR (prev_ciphertext XOR prev_plaintext))
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ciphertext_block = self.encrypt_block(xor_bytes(plaintext_block, xor_bytes(prev_ciphertext, prev_plaintext)))
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blocks.append(ciphertext_block)
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prev_ciphertext = ciphertext_block
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prev_plaintext = plaintext_block
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return b''.join(blocks)
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def decrypt_pcbc(self, ciphertext, iv):
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"""
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Decrypts `ciphertext` using PCBC mode and PKCS#7 padding, with the given
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initialization vector (iv).
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"""
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assert len(iv) == 16
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blocks = []
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prev_ciphertext = iv
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prev_plaintext = bytes(16)
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for ciphertext_block in split_blocks(ciphertext):
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# PCBC mode decrypt: (prev_plaintext XOR prev_ciphertext) XOR decrypt(ciphertext_block)
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plaintext_block = xor_bytes(xor_bytes(prev_ciphertext, prev_plaintext), self.decrypt_block(ciphertext_block))
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blocks.append(plaintext_block)
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prev_ciphertext = ciphertext_block
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prev_plaintext = plaintext_block
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return unpad(b''.join(blocks))
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def encrypt_cfb(self, plaintext, iv):
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"""
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Encrypts `plaintext` with the given initialization vector (iv).
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"""
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assert len(iv) == 16
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blocks = []
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prev_ciphertext = iv
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for plaintext_block in split_blocks(plaintext, require_padding=False):
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# CFB mode encrypt: plaintext_block XOR encrypt(prev_ciphertext)
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ciphertext_block = xor_bytes(plaintext_block, self.encrypt_block(prev_ciphertext))
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blocks.append(ciphertext_block)
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prev_ciphertext = ciphertext_block
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return b''.join(blocks)
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def decrypt_cfb(self, ciphertext, iv):
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"""
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Decrypts `ciphertext` with the given initialization vector (iv).
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"""
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assert len(iv) == 16
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blocks = []
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prev_ciphertext = iv
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for ciphertext_block in split_blocks(ciphertext, require_padding=False):
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# CFB mode decrypt: ciphertext XOR decrypt(prev_ciphertext)
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plaintext_block = xor_bytes(ciphertext_block, self.encrypt_block(prev_ciphertext))
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blocks.append(plaintext_block)
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prev_ciphertext = ciphertext_block
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return b''.join(blocks)
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def encrypt_ofb(self, plaintext, iv):
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"""
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Encrypts `plaintext` using OFB mode initialization vector (iv).
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"""
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assert len(iv) == 16
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blocks = []
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previous = iv
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for plaintext_block in split_blocks(plaintext, require_padding=False):
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# OFB mode encrypt: plaintext_block XOR encrypt(previous)
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block = self.encrypt_block(previous)
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ciphertext_block = xor_bytes(plaintext_block, block)
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blocks.append(ciphertext_block)
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previous = block
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return b''.join(blocks)
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def decrypt_ofb(self, ciphertext, iv):
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"""
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Decrypts `ciphertext` using OFB mode initialization vector (iv).
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"""
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assert len(iv) == 16
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blocks = []
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previous = iv
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for ciphertext_block in split_blocks(ciphertext, require_padding=False):
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# OFB mode decrypt: ciphertext XOR encrypt(previous)
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block = self.encrypt_block(previous)
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plaintext_block = xor_bytes(ciphertext_block, block)
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blocks.append(plaintext_block)
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previous = block
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return b''.join(blocks)
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def encrypt_ctr(self, plaintext, iv):
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"""
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Encrypts `plaintext` using CTR mode with the given nounce/IV.
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"""
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assert len(iv) == 16
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blocks = []
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nonce = iv
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for plaintext_block in split_blocks(plaintext, require_padding=False):
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# CTR mode encrypt: plaintext_block XOR encrypt(nonce)
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block = xor_bytes(plaintext_block, self.encrypt_block(nonce))
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blocks.append(block)
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nonce = inc_bytes(nonce)
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return b''.join(blocks)
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def decrypt_ctr(self, ciphertext, iv):
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"""
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Decrypts `ciphertext` using CTR mode with the given nounce/IV.
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"""
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assert len(iv) == 16
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blocks = []
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nonce = iv
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for ciphertext_block in split_blocks(ciphertext, require_padding=False):
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# CTR mode decrypt: ciphertext XOR encrypt(nonce)
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block = xor_bytes(ciphertext_block, self.encrypt_block(nonce))
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blocks.append(block)
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nonce = inc_bytes(nonce)
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return b''.join(blocks)
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__all__ = ["AES256"]
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