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Revision as of 10:33, 7 July 2016

SpyGEM coding

SpyGEM coding & crypting

Sub-coding: ​ ​

Message

Key

Formatted

Encoded

This page demonstrates the encoding and decoding of text messages into DNA, optionally with AES-256 encryption.

Enter a message into the Message field to have it encoded, or enter an encoded message into the Encoded field to have it decoded. The Key field is used for encryption & decryption and the Formatted field shows more details about the message block.

Different encodings for the message are possible. Both 'Six-four' and 'Ex-four' use 6 bits (3 base-pairs) per character, but are limited in the characters they allow. 'Six-four' allows only upper- and lower-case letters, digits, space and full-stop. 'Ex-four' is somewhat experimental and allows more characters (all of ASCII and a few more), but needs 12 bits for some characters, most notably for upper-case.

'Eight-bit' uses 8 bits (4 base-pairs) but allows every character.

The fully encoded message block is formatted as follows:

  1. The letters 'Spy' (always in 'Six-four'): 3 × 3 base pairs.
  2. The length of the encoded message: 16-bit number (8 base pairs).
  3. The checksum of the encoded message: 16-bit number (8 base pairs).
  4. The message: 3 - 4 base pairs per character.
  5. The letters 'GEM' (always in 'Six-four'): 3 × 3 base pairs.

The total overhead is 34 base pairs and the maximum message length is 65535 characters.

Encryption requires 'Eight-bit' as the sub-coding and has an additional 8 characters (32 base-pairs) overhead, regardless of key or message length.