The intention of these utilities are to allow recovery of BTSync keys at a later date by making them deterministic in a (hopefully) cryptographically secure way and also to create cryptographically secure directories of shares that could be stored in a relatively untrusted environment.

When BTSync generates a 1.4-style read-write key, it just requires a random, unique set of 20-bytes base32 encoded. If BTSync's natively generated keys have special mathematical properties, these utilities would undermine and potentially completely break the security behind BTSync. This cannot be easily verified as BTSync is a closed-source project.

Deterministic r/w keys are generated using the pbkdf2 algorithm using sha256 over a variable number of iterations. The root password and share name (used as a salt) with a desired key length of 20 bytes generates the bits needed for the key, which is then base32 encoded. An "A" is prepended if the share is not to be encrypted; a "D" is prepended if the share is to be encrypted.

Use ./btsync-keygen.py and you will be walked thru steps to generate a key. Preferribly, do this on a Linux or FreeBSD-based system to have Read-Only keys also retrieved using the included btsync binaries.

A directory contains shares with the name, iterations, and a description of shares. In addition, mechanisms for checking correct key are provided.

Each share's verifysalt is a randomly generated string to be used as a pbkdf2 salt against the correct password with the given iterations. Verify is the base64 encode of the payload of the pbkdf2 function.

It is assumed that base64.b32encode(os.urandom(65)) is secure enough when generating random strings for salts for directory listing password verification.