cryptutils

cryptutils

cryptutils is a set of common Go packages for doing encryption using NaCl and Ed25519 keys. It also includes a set of command line tools:

• secrets: command-line secrets manager
• otpc: command-line two-factor authentication token manager
• journal: password-backed journal
• passcrypt: password-based file encryption

The useful tools are all password-based at this time. secrets, otpc, and journal are all based on a common secret storage system. The secrets program provides a general-purpose secret management system; journal and otpc provide specialised interfaces for specific types of secrets (notes and TOTP/HOTP keys, respectively).

The programs are in the cmd/ subdirectory; each project has its own README.

The cryptography

cryptutils uses NaCl's secretbox (Salsa20 and Poly1305) for secret-key encryption, NaCl's box (Curve25519, Salsa20, and Poly1305) for public-key encryption, and Ed25519 for digital signatures. Typically, secret keys are derived in one of ways: via Scrypt, or via an ECDH exchange. For Scrypt, the parameters N=1048576, r=8, and p=1 are used. This makes generating keys using this expensive (typically, around 5 seconds on my 2.6 GHz i5 machine with 6G of RAM). When encrypting messages using public keys, an ephemeral key is generated for the encryption and a shared key is derived from this. The public key is prepended to the message for extraction by the recipient. When signing and encrypting using public keys, the message is signed before encrypting. The recipient will decrypt, then validate the signature.

NOTE: previous versions used N=32768, and will need to use the migrate-store utility to migrate the store over (or use the previous versions).

Motivation and history

I hated depending on my phone for managing two-factor authentication (I prefer to not carry it around), which led to the first iteration of otpc. This used Scrypt and NaCl to secure the tokens. Later, I wanted a password manager that I could use on the command-line and send passwords to xclip (or pbcopy if I was on a Mac); the first iteration of password copied the crypto.go file from otpc. Finally, I wanted to replace sshcrypt with a NaCl/Ed25519-based system; at this point, I realised that it would be easier to refactor the crypto components into a common set of packages. This included building a generalised keyring for fcrypt and, realising that the same data structure lent itself well to password and otpc, a common datastore for secrets. Eventually, passwords was renamed to secrets when I began to use it for manipulating the otpc store, letting me keep a lot of unnecessary functionality out of otpc. At some point, I realised the datastore could also be used for storing journal entries, and added a journaling front end.

Dependencies

• golang.org/x/crypto
• github.com/agl/ed25519
• github.com/conformal/yubikey
• github.com/gokyle/readpass

License

cryptutils is licensed under the ISC license.