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| 1 | +#!/usr/bin/env python |
| 2 | +#Takes a string as an argument and returns 3 base64 encoded string partials. |
| 3 | +#One of these strings is guaranteed to be present in the base64 content if |
| 4 | +#the original plain-text code contained the (case-sensitive) input string. |
| 5 | + |
| 6 | +#Due to the 8 bit to 6 bit encoding conversion involved in base64 encoding, |
| 7 | +#the edges don't always align nicely, so trimming is required as the first |
| 8 | +#and last characters may be different depending on the immediate context. |
| 9 | + |
| 10 | +from base64 import b64encode |
| 11 | +import sys |
| 12 | + |
| 13 | +def main(input): |
| 14 | + L_offset = 0 |
| 15 | + R_offset = 3 - ((len(input) + L_offset) % 3) |
| 16 | + if (R_offset == 3): |
| 17 | + R_offset = 0 |
| 18 | + |
| 19 | + e1, e2, e3 = encode(input) |
| 20 | + |
| 21 | + e1 = trim(e1, L_offset, R_offset) |
| 22 | + |
| 23 | + L_offset += 1 |
| 24 | + R_offset = 3 - ((len(input) + L_offset) % 3) |
| 25 | + if (R_offset == 3): |
| 26 | + R_offset = 0 |
| 27 | + |
| 28 | + e2 = trim(e2, L_offset, R_offset) |
| 29 | + |
| 30 | + L_offset += 1 |
| 31 | + R_offset = 3 - ((len(input) + L_offset) % 3) |
| 32 | + if (R_offset == 3): |
| 33 | + R_offset = 0 |
| 34 | + |
| 35 | + e3 = trim(e3, L_offset, R_offset) |
| 36 | + |
| 37 | + print(e1) |
| 38 | + print(e2) |
| 39 | + print(e3) |
| 40 | + |
| 41 | +def offset_2_chars(offset): |
| 42 | + if (offset == 0): |
| 43 | + return 0 |
| 44 | + elif (offset == 1): |
| 45 | + return 2 |
| 46 | + else: |
| 47 | + return 3 |
| 48 | + |
| 49 | +def trim(input, L_offset, R_offset): |
| 50 | + input = trimL(input, L_offset) |
| 51 | + input = trimR(input, R_offset) |
| 52 | + return input |
| 53 | + |
| 54 | +def trimL(input, offset): |
| 55 | + left_cut = offset_2_chars(offset) |
| 56 | + return input[left_cut:] |
| 57 | + |
| 58 | +def trimR(input, offset): |
| 59 | + if (offset == 0): |
| 60 | + return input |
| 61 | + right_cut = offset_2_chars(offset) |
| 62 | + return input[:-right_cut] |
| 63 | + |
| 64 | +def encode(input): |
| 65 | + e1 = b64encode(input) |
| 66 | + e2 = b64encode('0' + input) |
| 67 | + e3 = b64encode('00' + input) |
| 68 | + return e1, e2, e3 |
| 69 | + |
| 70 | +if __name__ == '__main__': |
| 71 | + main(sys.argv[1]) |
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