misc: add text scrambler

A small program that randomly flips bits in a string,
limited to printable characters

This is intended for generating messed up text for corrupted communication

misc/bit_scrambler.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+
+import sys, random
+
+def bitflip(byte, bit):
+    bits = [
+        0b00000001,
+        0b00000010,
+        0b00000100,
+        0b00001000,
+        0b00010000,
+        0b00100000,
+        0b01000000,
+        0b10000000
+    ]
+    negbits = [
+        0b11111110,
+        0b11111101,
+        0b11111011,
+        0b11110111,
+        0b11101111,
+        0b11011111,
+        0b10111111,
+        0b01111111
+    ]
+    if byte | bits[bit] == byte:
+        return byte & bits[bit]
+    return byte | bits[bit]
+
+def n_bits_off(byte, n):
+    if n>8:
+        raise Error
+
+    bits = []
+
+    while len(bits) < n:
+        bit = random.randint(0,7)
+        if bit in bits:
+            continue
+        bits.append(bit)
+
+    for bit in bits:
+        byte = bitflip(byte, bit)
+
+    return byte
+
+
+if __name__ == "__main__":
+    if not len(sys.argv) == 2:
+        print("This program takes exactly one argument: the string to scramble.")
+
+    output = []
+    for character in list(sys.argv[1]):
+        a = random.randint(0, 36)
+        if ord(character)<33 or ord(character) > 126:
+            output.append(character)
+        elif a%18==0:
+            byte = n_bits_off(ord(character), 3)
+            if byte > 32 and byte < 127:
+                output.append(chr(byte))
+            else:
+                output.append(character)
+        elif a%12==0:
+            byte = n_bits_off(ord(character), 2)
+            if byte > 32 and byte < 127:
+                output.append(chr(byte))
+            else:
+                output.append(character)
+        elif a%9==0:
+            byte = n_bits_off(ord(character), 1)
+            if byte > 32 and byte < 127:
+                output.append(chr(byte))
+            else:
+                output.append(character)
+        else:
+            output.append(character)
+
+    print("".join(output))