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update the README

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Mirek Kratochvil 2018-04-12 10:17:14 +02:00
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README.md
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@ -70,8 +70,8 @@ You may as well see the paper [1], there are also pictures. This is somewhat mor
3. Find the next letter you want to encrypt on the board, its position is `P`. 3. Find the next letter you want to encrypt on the board, its position is `P`.
4. Look at the marker; numbers written on the marked tile are coordinates `M`. 4. Look at the marker; numbers written on the marked tile are coordinates `M`.
5. Compute position of the ciphertext as `C := P + M mod (7,7)`. Output the letter found on position `C` as ciphertext. 5. Compute position of the ciphertext as `C := P + M mod (7,7)`. Output the letter found on position `C` as ciphertext.
6. Rotate the row that contains the plaintext letter one position to the right, carry the marker if present. 6. Rotate the row that contains the plaintext letter one position to the right, but do not carry the marker if present (it should stay on the same coordinates).
7. Rotate the column that now (after the first rotation) contains the ciphertext letter one position down, carry the marker if present. 7. Rotate the column that now (after the first rotation) contains the ciphertext letter one position down, also not carrying the marker.
8. Update the position of the marker: `M := M + C' mod (7,7)` where `C'` are the numbers written on the ciphertext tile. 8. Update the position of the marker: `M := M + C' mod (7,7)` where `C'` are the numbers written on the ciphertext tile.
9. Repeat from 3 as many times as needed to encrypt the whole plaintext. 9. Repeat from 3 as many times as needed to encrypt the whole plaintext.
@ -90,7 +90,7 @@ You may as well see the paper [1], there are also pictures. This is somewhat mor
+ * 7 8 9 , - + * 7 8 9 , -
5. Ciphertext is 'w' 6. Rotate the plaintext 1 position 5. Ciphertext is 'w' 6. Rotate the plaintext 1 position
(='y' moved by (5,0)) right, possibly carrying the marker. (='y' moved by (5,0)) right, keep marker coordinates.
[e]f _ a b c d [e]f _ a b c d [e]f _ a b c d [e]f _ a b c d
Output 'w'! l m g h i j k l m g h i j k Output 'w'! l m g h i j k l m g h i j k
@ -102,7 +102,7 @@ You may as well see the paper [1], there are also pictures. This is somewhat mor
7. Rotate the ciphertext 1 Now look at the ciphertext tile: 7. Rotate the ciphertext 1 Now look at the ciphertext tile:
position down, also carry. position down.
[e]f _ a b , d /-----\ [e]f _ a b , d /-----\
l m g h i c k | | l m g h i c k | |
@ -174,9 +174,9 @@ letters of a pre-negotiated length (e.g. N tiles drawn randomly from a bag,
adviseable value of N is at least 10). adviseable value of N is at least 10).
You may also want to add a random number of spaces to the end of the ciphertext You may also want to add a random number of spaces to the end of the ciphertext
-- it prevents the enemy from seeing the difference between ciphertexts of -- it prevents the enemy from seeing the difference between ciphertexts of 'yes
'yes please' and 'no', which would otherwise encrypt to easily measurable please' and 'no', which would otherwise encrypt to gibberish that is easily
gibberish like `qwc3w_cs'(` and `+v`. distinguishable by length, like `qwc3w_cs'(` and `+v`.
### Authenticated encryption ### Authenticated encryption