Updated scripts and added new

rc4.py

@@ -0,0 +1,108 @@
+import logging
+from argparse import ArgumentParser
+from pathlib import Path
+
+_VERBOSE_SBOX = False
+_VERBOSE_PRGA = False
+_STEPWISE_PRGA = False
+
+
+def sbox(key: list[int]) -> list[int]:
+    """
+    Creates and permutates the substitution box given a key.
+    """
+    # create sbox
+    S = [i for i in range(256)]
+
+    # permutate sbox
+    j = 0
+    for i in range(256):
+        j = (j + S[i] + key[i % len(key)]) % 256
+        if _VERBOSE_SBOX:
+            print(f"Swapping S[{i=:3d}] = {S[i]:3d} and S[{j=:3d}] = {S[j]:3d}.")
+        S[i], S[j] = S[j], S[i]  # swap
+
+    return S
+
+
+def prga(text: list[int], S: list[int]) -> list[int]:
+    """
+    Encrypts/Decrypts text given a substitution box.
+    """
+    text = list(text)
+    i = 0
+    j = 0
+    for x in range(len(text)):
+        i = (i + 1) % 256
+        j = (j + S[i]) % 256
+
+        if _VERBOSE_PRGA:
+            print(f"Swapping S[{i=:3d}] = {S[i]:3d} and S[{j=:3d}] = {S[j]:3d}.")
+
+        if _STEPWISE_PRGA:
+            try:
+                input("Press ENTER to continue ...")  # Step through
+            except KeyboardInterrupt:
+                print("KeyboardInterrupt.")
+                exit(0)
+
+        S[i], S[j] = S[j], S[i]  # swap
+        K = S[(S[i] + S[j]) % 256]
+        text[x] ^= K
+    return text
+
+
+def convert(text: bytes | list[int]) -> bytes | list[int]:
+    """
+    Converts text from bytes -> list[int] and back.
+    """
+    if isinstance(text, bytes):
+        return [int(c) for c in text]
+    elif isinstance(text, list):
+        return bytes(text)
+    else:
+        raise ValueError(f"Unsupported input type '{type(text)}'")
+
+
+def rc4(in_file: str | Path, out_file: str | Path, key_file: str | Path):
+    """
+    Execute the RC4 encryption/decryption algorithm on the input file,
+    creating the output file using the contents from the key file.
+    """
+
+    with open(key_file, "rb") as key_file:
+        S = sbox(convert(key_file.read()))
+
+    with open("sbox_solution", "wb") as fd:
+        fd.write(convert(S))
+
+    # read input
+    with open(in_file, "rb") as data_in_file:
+        data_in = data_in_file.read()
+
+    data_in = convert(data_in)  # bytes -> list[int]
+    data_out = prga(data_in, S)
+    data_out = convert(data_out)  # list[int] -> bytes
+
+    # write output
+    with open(out_file, "wb") as data_out_file:
+        data_out_file.write(data_out)
+
+
+if __name__ == "__main__":
+    parser = ArgumentParser(
+        description="Encrypts plaintext using the RC4 encryption algorithm, or decrypts RC4 ciphertext (based on input)"
+    )
+    parser.add_argument("input", type=str, help="Input file")
+    parser.add_argument("key", type=str, help="Key file")
+    parser.add_argument("output", type=str, help="Output file")
+    parser.add_argument("--verbose-sbox", const=True, default=False, action="store_const", help="Show S-Box swaps")
+    parser.add_argument("--verbose-prga", const=True, default=False, action="store_const", help="Show PRGA swaps")
+    parser.add_argument("--step-prga", const=True, default=False, action="store_const", help="Step-by-step PRGA swaps")
+    args = parser.parse_args()
+
+    _VERBOSE_SBOX = args.verbose_sbox
+    _VERBOSE_PRGA = args.verbose_prga
+    _STEPWISE_PRGA = args.step_prga
+
+    rc4(args.input, args.output, args.key)