playfair is fairly easy to break using frequency analysis, especially wi
th modern computers. Because
the same digram will always encode to
the same pair of letters, it doesn't significantly increase
the brute force necessary. If you have a sample of plaintext and its equivalent ciphertext key extraction is trivial. If you have enough ciphertext frequency analysis is straight froward. Cribs can also be used, as wi
th any substitution cipher. For example, in any leng
thy english text
the letters th will appear very often.
Now if you want a real challenge, try this cipher I recently sent to a friend at NSA
-
9a af 4e 54 67 03 b7 ab 23 4a 01 eb ff 5c e0 7b 4f e6 39 2f fa 5e 97 43 ee 05 eb 3e a6 28 7e 7f c6 cf f3 e5 a1 b4 62 09 fd e2 56 1a 82 e7 59 c4 84 49 32 23 67 bf 87 7f 18 b8 32 41 c3 4b 82 c3 af c1 fc 53 ad ce 97 ad 15 15 5a 0f f7 2d b9 97 8a 6e d2 7f 01 42 f7 6f 7a a2 ab 89 9a e1 57 6d 9b f2 46 67 d5 f8 2a 2f 8d db aa 48 22 5d 22 23 5f 06 c7 97 fc b5 52 38 26 14 8c 15 7a 87 fe 5b 33 32 88 80 0f dd 9c b0 14 b3 19 3b 43 b9 53 8b 33 8b 13 83 fc 14 b3 dc 67 40 26 d5 0b cf 2a ed da c1 44 a6 88 07 f2 06 43 50 0a ce 6d b7 0b cb 78 90 4f 76 54 bd f7 9e 27 3e e5 a5 81 43 1c 8b b1 b7 34 b7 36 1e 2a c0 f4 8f cb dd b5 f8 c2 e3 0d ed 80 0e 97 d6 b0 09 d2 7a bc 44 07 d6 c8 df 56 70 b3 e8 77 52 d5 05 bd 26 50 c5 d3 79 38 7d 12 45 f9 d8 08 3e 54 78 e7 5d ce c4 3f 59 4f a9 4c bf 22 83 6d 31 19 07 0e e7 28 72 ef 29 45 20 0e f6 48 de 9c 8b 4b 25 04 27 16 3b 9b 30 a8 ff 58 0e 05 4c ab 13 a9 e8 62 e4 17 ec e8 d7 d2 f2 e8 0b fe 9c 65 28 22 77 a2 32 95 a4 ed de 34 0d c3 3d 03 71 26 37 82 30 e2 1b 08 84 3e 5b c0 91 c2 c3 65 32 f7 9e 10 7a 5a 75 21 2f 68 c3 86 d5 72 24 a5 24 44 1e 1c 7e 9a d9 ac f8 48 0b f7 6e 48 6e 0d 4e 82 c5 72 f4 37 f1 9f 47 0f db c6 2f 38 3f 94 56 25 4d e0 f1 76 9f ee 9b 92 9e dc f4 a0 86 63 06 f7 e2 f7 09 4b 2f 18 bd fe 7a 55 0e 97 3d 1f 8e df ef 2d b3 e7 6f f4 ad 64 ec e3 4f 10 8c bf f0 71 9a b1 11 a2 ff 87 f3 f5 c1 e3 ff a6 2a e1 b3 c0 ea d1 91 6a c3 35 16 28 e0 f4 cd b4 47 cb 20 0a 69 93 6d 13 b0 44 82 a5 cd 43 ee d2 1e 97 4e d1 ec 5e 34 c7 d5 80 84 43 11 c7 32 d9 c6 da e7 9c 36 e3 75 fb 22 74 af 7e 57 6f 73
It is text, taken from a classic novel.
It is English
The cipher is not a one time pad