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| author | Trevor Terris <tkterris@gmail.com> | 2021-04-22 14:51:04 +0200 |
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| committer | Trevor Terris <tkterris@gmail.com> | 2021-04-22 14:51:04 +0200 |
| commit | 8e4e169a395257be63a80d732e6d127a53ea9976 (patch) | |
| tree | 4d1eb92343c2104b46afaff9257caff87f6b1d64 | |
| parent | 00f89c47c7963c8873bee38a1d003d1cec443c5c (diff) | |
| download | ls47-8e4e169a395257be63a80d732e6d127a53ea9976.tar.gz ls47-8e4e169a395257be63a80d732e6d127a53ea9976.tar.bz2 | |
Moved alternative board to a new "modifications" section
| -rw-r--r-- | README.md | 114 |
1 files changed, 58 insertions, 56 deletions
@@ -63,62 +63,6 @@ To run (hand-run) the encryption/decryption, you will also need some kind of a marker (e.g. a small shiny stone, bolt nut or similar kind of well-shaped trash). -#### Alternative playing-card-compatible board - -The following board can be used so that characters and offsets can be easily -mapped to playing cards, similar to the Solitaire cipher [2]. Using playing -cards could be more innocuous and easily explainable to the secret police than -a set of peculiar numbered tiles. - -``` -0 a b c d e f -g h i j k l m -n o p q r s t -u v w x y z _ -. , - + * / : -? ! ' ( ) 1 2 -3 4 5 6 7 8 9 -``` - -With this layout, the following mapping to playing cards is used: - -| **Character** | Card | Index | **Character** | Card | Index | **Character** | Card | Index | **Character** | Card | Index | -|-----------|------|-------|-----------|------|-------|-----------|------|-------|-----------|------|--------| -| a | A♦ | 1 | n | A♣ | 14 | _ | A♥ | 27 | 1 | A♠ | 40 | -| b | 2♦ | 2 | o | 2♣ | 15 | . | 2♥ | 28 | 2 | 2♠ | 41 | -| c | 3♦ | 3 | p | 3♣ | 16 | , | 3♥ | 29 | 3 | 3♠ | 42 | -| ... | ... | ... | ... | ... | ... | ... | ... | ... | ... | ... | ... | -| j | 10♦ | 10 | w | 10♣ | 23 | ! | 10♥ | 39 | 7 | 7♠ | 46 | -| k | J♦ | 11 | x | J♣ | 24 | ' | J♥ | 39 | 8 | 8♠ | 47 | -| l | Q♦ | 12 | y | Q♣ | 25 | ( | Q♥ | 39 | 9 | 9♠ | 48 | -| m | K♦ | 13 | z | K♣ | 26 | ) | K♥ | 39 | 0 | 10♠ | 49 (0) | - -The (x, y) offset can be calculated by first determining the index: take the -number of the suit (0-3), multiply by 13, and add the card number (using 1 for -the Ace, 11-13 for face cards). Then, determine the offset from the index -using the usual modular arithmetic: `x = index % 7` and `y = index / 7`. - -Alphanumeric characters can be easily mapped to cards, with letters mapping to -Diamonds or Clubs and numbers mapping to Spades (note that Spades face cards -are ommitted). All of the special characters are mapped to the Hearts, though -coming up with a mnemonic for the mapping of each special character to each -Heart is left as an exercise for the reader. - -For LC4, the following board could be used: - -``` -# a b c d e -f g h i j k -l m n o p q -r s t u v w -x y z _ 2 3 -4 5 6 7 8 9 -``` - -The "Hearts" suit would be ommitted from the card mapping table, and the index -of each of the Spades would be decreased by 13 to compensate. `#` and `_` -would map to 10♠ and A♠, respectively. - ## How-To You may as well see the paper [1], there are also pictures. This is somewhat more concentrated: @@ -198,6 +142,8 @@ stays the same. Grab a bag full of tiles and randomly draw them one by one. Key is the 49-item permutation of them. +## Modifications + ### Key expansion from a password Remembering 49-position random permutation that includes weird characters is @@ -252,6 +198,62 @@ This works because the cipher output is message-dependent: Having a wrong bit somewhere in the middle causes avalanche effect and erases any meaning from the text after several characters. +### Alternative playing-card-compatible board + +The following board can be used so that characters and offsets can be easily +mapped to playing cards, similar to the Solitaire cipher [2]. Using playing +cards could be more innocuous and easily explainable to the secret police than +a set of peculiar numbered tiles. + +``` +0 a b c d e f +g h i j k l m +n o p q r s t +u v w x y z _ +. , - + * / : +? ! ' ( ) 1 2 +3 4 5 6 7 8 9 +``` + +With this layout, the following mapping to playing cards is used: + +| **Character** | Card | Index | **Character** | Card | Index | **Character** | Card | Index | **Character** | Card | Index | +|-----------|------|-------|-----------|------|-------|-----------|------|-------|-----------|------|--------| +| a | A♦ | 1 | n | A♣ | 14 | _ | A♥ | 27 | 1 | A♠ | 40 | +| b | 2♦ | 2 | o | 2♣ | 15 | . | 2♥ | 28 | 2 | 2♠ | 41 | +| c | 3♦ | 3 | p | 3♣ | 16 | , | 3♥ | 29 | 3 | 3♠ | 42 | +| ... | ... | ... | ... | ... | ... | ... | ... | ... | ... | ... | ... | +| j | 10♦ | 10 | w | 10♣ | 23 | ! | 10♥ | 39 | 7 | 7♠ | 46 | +| k | J♦ | 11 | x | J♣ | 24 | ' | J♥ | 39 | 8 | 8♠ | 47 | +| l | Q♦ | 12 | y | Q♣ | 25 | ( | Q♥ | 39 | 9 | 9♠ | 48 | +| m | K♦ | 13 | z | K♣ | 26 | ) | K♥ | 39 | 0 | 10♠ | 49 (0) | + +The (x, y) offset can be calculated by first determining the index: take the +number of the suit (0-3), multiply by 13, and add the card number (using 1 for +the Ace, 11-13 for face cards). Then, determine the offset from the index +using the usual modular arithmetic: `x = index % 7` and `y = index / 7`. + +Alphanumeric characters can be easily mapped to cards, with letters mapping to +Diamonds or Clubs and numbers mapping to Spades (note that Spades face cards +are ommitted). All of the special characters are mapped to the Hearts, though +coming up with a mnemonic for the mapping of each special character to each +Heart is left as an exercise for the reader. + +For LC4, the following board could be used: + +``` +# a b c d e +f g h i j k +l m n o p q +r s t u v w +x y z _ 2 3 +4 5 6 7 8 9 +``` + +The "Hearts" suit would be ommitted from the card mapping table, and the index +of each of the Spades would be decreased by 13 to compensate. `#` and `_` +would map to 10♠ and A♠, respectively. + ## References [1] *Kaminsky, Alan. "ElsieFour: A Low-Tech Authenticated Encryption Algorithm For Human-to-Human Communication." IACR Cryptology ePrint Archive 2017 (2017): 339.* |