Keyper

A basic password manager with a TUI interface.

Storage

The sled database is used for on-disk storage. However, sled does not natively support encryption.

Instead, we use an encryption scheme composed from well-tested primitives implemented in the RustCrypto cryptographic libraries.

Salt Encryption

A salt is a cryptographic value used to add randomness to inputs, and is commonly used in key-derivation algorithms.

We use the following scheme for password-based key derivation (in pseudo-code):

SALT = {random 32-bytes}
PASSWORD = {user-input password}
ENCRYPTION_KEY = sha3::TurboShake256::hash(SALT | PASSWORD);

However, we also want to keep the salt value secret when storing to disk (maybe a bit of paranoia is a good thing? :3)

The following scheme is used to encrypt the salt for storage (in pseudo-code):

SALT = {zeroes 32-bytes}
PASSWORD = {user-input password}

SALT_KEY = sha3::TurboShake256::hash(SALT | PASSWORD);
SALT_NONCE = {random 12-bytes}

ENCRYPTED_SALT = chacha20poly1305::encrypt(SALT_KEY, SALT_NONCE, SALT)

The entry is then stored in the database as:

SALT_DB_KEY = sha3::TurboShake256::hash("salt");
sled::Db::insert(SALT_DB_KEY, SALT_NONCE | ENCRYPTED_SALT);

Entry Encryption

Entries are encrypted in much the same way, with the slight change that the fields need to be length-prefix encoded.

We currently use 32-bit, little-endian length fields.

TITLE = Entry.title;
CONTENT = Entry.content;
TITLE_LEN = (TITLE.len() as u32).to_le_bytes();
CONTENT_LEN = (CONTENT.len() as u32).to_le_bytes();
ENTRY_NONCE = {random 12-bytes}
ENTRY_INDEX = EntryList.len()
ENTRY_PLAINTEXT = TITLE_LEN | TITLE | CONTENT_LEN | CONTENT

ENTRY_DB_KEY = sha3::TurboShake256::hash(ENTRY_INDEX)
ENCRYPTED_ENTRY = chacha20poly1305::encrypt(ENCRYPTION_KEY, ENTRY_NONCE, ENTRY_PLAINTEXT)

sled::Db::insert(ENTRY_DB_KEY, ENTRY_NONCE | ENCRYPTED_ENTRY) 

Using the length-prefixed value encoding is very common, and allows for extending the Entry fields almost indefinitely.

By using the AEAD ChaCha20Poly1305 algorithm, we also get the benefit of database corruption protection.

If someone messes with your database entries, they won't decrypt properly.

Credits

• TUI powered by ratatui + crossterm
• Crypto provided by RustCrypto
• Storage provided by sled
• TOTP provided by totp-rs
• Clipboard support provided by crossterm + arboard
• Keepass support provided by keepass

Fuck AI

This application was made with 100% human engineering, entirely without the aid of LLMs.