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ExEF v2

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This version has been deprecated in favour of v3 since Excalibur 0.3. This document is reproduced here only for posterity.

The following is a diagram of the ExEF format. The numbers represent 0-indexed byte positions.

  • Bytes 0 to 3 will be the ExEF magic constant: the ASCII string ExEF.
  • Bytes 4 and 5 represent the ExEF version, which should be interpreted as an 2-byte unsigned integer.
    • The current version is 00 02.
  • Bytes 6 and 7 represent the AES-GCM key size, which should be interpreted as an 2-byte unsigned integer. There are currently only 3 supported values.
    • The bytes 00 80 represent aes-128-gcm.
    • The bytes 00 C0 represent aes-192-gcm.
    • The bytes 01 00 represent aes-256-gcm.
  • Bytes 8 to 19 represent the 12-byte nonce used for AES-GCM encryption.
  • Bytes 20 to 27 represent the ciphertext length, which should be interpreted as an 8-byte unsigned integer.
  • The ciphertext follows.
  • The last 16 bytes is the 16-byte AES-GCM tag.