first commit

.gitignore

@@ -0,0 +1,3 @@
+**/.vscode
+**/__pycache__
+**/.DS_Store

README.md

@@ -0,0 +1,9 @@
+# Advanced Encryption Standard (AES)
+
+This repository provides a simple implementation of AES using python and numpy. This implementation is as explained in the textbook [Understanding Cryptography](https://doi.org/10.1007/978-3-642-04101-3) by Christof Paar & Jan Pelzl. It should be noted that this implementation was created for learning purposes. For security usage, well-established packages should be used.
+
+## Examples
+
+```Python
+print('hello world')
+```

aes.py

@@ -0,0 +1,23 @@
+import numpy as np
+from numpy.typing import NDArray
+
+
+from key_schedule import key_schedule
+from byte_substitution import s
+from shift_rows import shift_rows
+from mix_column import mix_column
+
+
+def aes_128(x: NDArray[np.unit8], k: NDArray[np.unit8]):
+    key_generator = key_schedule(k)
+    state = x
+    state ^= next(key_generator)
+
+    # TODO: remove mix_column form the last step
+    for key in key_generator:
+        state = s(state)
+        state = shift_rows(state)
+        state = mix_column(state)
+        state ^= key
+
+    return state

byte_substitution.py

@@ -0,0 +1,9 @@
+import numpy as np
+from numpy.typing import NDArray
+
+
+from s_box import s_box
+
+
+def s(a: NDArray[np.uint8]):
+    return np.array([s_box[ai] for ai in a])

key_schedule.py

@@ -0,0 +1,43 @@
+import numpy as np
+from numpy.typing import NDArray
+
+from s_box import s_box
+
+
+RC = (
+    0b0000_0001,
+    0b0000_0010,
+    0b0000_0100,
+    0b0000_1000,
+    0b0001_0000,
+    0b0010_0000,
+    0b0100_0000,
+    0b1000_0000,
+    0b0001_1011,
+    0b0011_0110,
+)
+
+
+def g(v: NDArray[np.uint8], i: int):
+    rotated = np.roll(v, -1)
+
+    substituted = np.array([
+        s_box[xi]
+        for xi in rotated
+    ])
+
+    substituted[0] ^= RC[i]
+
+    return substituted
+
+
+def key_schedule(k: NDArray[np.uint8]):
+    w = np.split(k, 4)
+    yield np.concatenate(w)
+
+    for i in range(10):
+        w[0] ^= g(w[-1], i)
+        w[1] ^= w[0]
+        w[2] ^= w[1]
+        w[3] ^= w[2]
+        yield np.concatenate(w)

mix_column.py

@@ -0,0 +1,51 @@
+import numpy as np
+from numpy.typing import NDArray
+
+
+constant_matrix = np.array([
+    [0x02, 0x03, 0x01, 0x01],
+    [0x01, 0x02, 0x03, 0x01],
+    [0x01, 0x01, 0x02, 0x03],
+    [0x03, 0x01, 0x01, 0x02],
+])
+
+
+def gf_multiply(x, y):
+    r = 0
+
+    for _ in range(8):
+        if y & 1:
+            r ^= x
+
+        hi_bit_set = x & 0x80
+        x <<= 1
+
+        if hi_bit_set:
+            x ^= 0x11b
+
+        y >>= 1
+
+    return r & 0xFF
+
+
+def finite_field_256_dot(v: NDArray[np.uint8], u: NDArray[np.uint8]):
+    result = 0
+
+    for vi, ui in zip(v, u):
+        if ui == 0x01:
+            result ^= vi
+        else:
+            result ^= gf_multiply(vi, ui)
+
+    return result
+
+
+def mix_column(b: NDArray[np.uint8]):
+    reshaped = b.reshape((4, 4))
+
+    result = np.array([
+        finite_field_256_dot(reshaped[:, i], constant_matrix[i])
+        for i in range(4)
+    ])
+
+    return result.reshape((16,))

s_box.py

@@ -0,0 +1,21 @@
+import numpy as np
+
+
+s_box = np.array([
+    0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5, 0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76,
+    0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0,
+    0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC, 0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15,
+    0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A, 0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75,
+    0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84,
+    0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B, 0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF,
+    0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8,
+    0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5, 0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,
+    0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73,
+    0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88, 0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB,
+    0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79,
+    0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9, 0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08,
+    0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A,
+    0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E, 0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E,
+    0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94, 0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF,
+    0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16
+], np.uint8)

shift_rows.py

@@ -0,0 +1,11 @@
+import numpy as np
+from numpy.typing import NDArray
+
+
+def shift_rows(b: NDArray[np.uint8]):
+    shifted = b.reshape((4, 4))
+
+    for i in range(4):
+        shifted[i] = np.roll(shifted, -i)
+
+    return shifted.reshape((16,))