CIPHERCipher Tracker: encrypted habit tracking. Your phone encrypts every entry with AES-256 before it reaches us.

Every entry we hold is sealed like this

• v3:3 chars

  Format marker. PBKDF2 with the iteration count stored per blob.

• iterations8 chars

  200,000 iterations for new writes. Encoded in the blob and covered by the signature, so it cannot be lowered without breaking it.

• IV32 chars

  A fresh 128-bit initialisation vector for every write.

• ciphertext

  AES-256-CTR. The key is derived from your password, on your phone.

• HMAC-SHA25632 chars

  Signs the iteration count, IV and ciphertext; the first 128 bits of the signature are kept. Changing any of them breaks it.

Stored as one sealed record per calendar month, labelled with the year and month.