Protocol / Seal
Encrypt before the network.
The sensitive step happens locally. Your browser turns the passphrase into an encryption key and seals vault content before storage ever sees it.
Cipher
AES-256-GCM
Confidentiality plus tamper detection
KDF
PBKDF2
SHA-256, 250,000 iterations
Server plaintext
0 bytes
The key never leaves the browser
01Passphrase
02PBKDF2-SHA256
03AES-256 key
04AES-GCM seal
05Ciphertext
Design ruleMinimize what infrastructure can know. Make the unavoidable trade-offs visible.
01 / DERIVE
The passphrase is stretched locally into a vault key.
SEES uses a per-vault salt and PBKDF2-SHA256 to make brute-force attempts more expensive. The derived AES key is kept in browser memory while the vault is unlocked.
Per-vault salt250k iterationsMemory only
02 / SEAL
Every write is authenticated ciphertext.
AES-256-GCM protects both confidentiality and integrity. If encrypted data is modified in storage or transit, decryption fails instead of returning silently corrupted content.
Authenticated encryptionTamper detectionUnique nonce per seal
03 / LIMIT
Strong cryptography still depends on the device you use.
Local encryption protects against server-side exposure, but it cannot save a compromised browser, malicious extension, or weak passphrase. The security model is powerful because it is honest about that boundary.
Device trust mattersUse strong passphrasesNo magic claims
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