The Tokens area contains a number of entries. Each entry has the following format:
Magic: 0x4e4b4f54 'TOKN' Version: 0x00000001 Length: 0x???????? Length of the data area Generation: 0x00000001 CRC: 0x???????? CRC of the full entry treating the 4 CRC bytes as zeroes Name: up to 16 bytes, zero padded name of the token Data: 'lenght' bytes, plus zero padding up to the next 4 bytes boundary
The CRC polynomial is 0xedb88320.
In the webOS-Internals git repository  you will find a little utility which reads and sets bootie tokens and env variables as well as restore backup tokens.