Encrypted before it leaves the phone
Card numbers, barcodes, PINs, and notes are encrypted on your device with ChaCha20-Poly1305. What reaches CardWarden's server is ciphertext. A copy of the database, or a breach of the host, does not hand anyone readable cards.
Keys stay with you
The key that decrypts your cards is wrapped by a key derived from your master password or your recovery phrase, using PBKDF2-HMAC-SHA256 with 600,000 iterations. CardWarden does not have a copy of that password or phrase, so we cannot open the vault for you, for a retailer, or for an advertiser.
What this page leaves out
Sharing, family pockets, and backup each use their own wrapped keys. The diagrams, iteration counts, and threat model live in the security white paper. This page is the short version: your cards are encrypted on the device, and the server cannot read them.
