dvx

Package dvx provides an easy-to-use interface to a Cryptography service, that uses state-of-the-art primitives. It provides 4 main categories of supported operations: Encryption/Decryption, Signing/Verifying, MAC, and as a special higher-order algorithm: TOTP Creation/Verification.

(See the picture of the complete architecture here)

Specification

Encoding

dvx has built-in support for upgrading the underlying cryptographic primitives used. It therefore introduces its packaging format for results from a dvx.Protocol instance:

<version>.<type_prefix>.<data>

1. Version: Is the version of the underlying primitives and the way how keys are derived from the KeyPool for there respective primitives.
2. TypePrefix: Is the identifier of the module used: "enc", "sig", "tag" or "totp"
3. Data: is the raw data (e.g. encrypted content, signature, mac tag, etc.) represented as base64 url string without padding append ("Raw" encoding).

Primitives

dv1

• Authenticated Encryption: XChaCha20-Poly1305 (192-bit random nonce, 256-bit key, 128-bit authentication tag)
  1. Generate 24 random bytes using a CSPRNG as nonce
  2. Pack "dv1" version string and nonce into AEAD-additional data (append([]byte("dv1"), nonce...))
  3. Use AEAD construction with key, nonce, message, additional_data
• MAC: Keyed Blake2b (512-bit key, 256-|512-bit tag)
• Signatures: Ed25519 (EdDSA over Curve25519)
• Key Derivation: Argon2id (512-bit derived key)

Further reading

A few links and resources that should explain why the selected primitives where chosen for dv1

• General:
  • https://loup-vaillant.fr/articles/crypto-is-not-magic
  • https://latacora.micro.blog/2018/04/03/cryptographic-right-answers.html
  • https://paragonie.com/blog/2019/03/definitive-2019-guide-cryptographic-key-sizes-and-algorithm-recommendations
  • https://monocypher.org/
• XChaCha20-Poly1305:
  • https://doc.libsodium.org/secret-key_cryptography/aead/chacha20-poly1305/xchacha20-poly1305_construction
  • https://datatracker.ietf.org/doc/html/rfc8439
  • https://monocypher.org/manual/aead
  • https://crypto.stackexchange.com/questions/91945/xsalsa20poly1305-for-encryption-at-rest
  • https://github.com/paseto-standard/paseto-spec/blob/master/docs/01-Protocol-Versions/Version2.md
  • https://github.com/paseto-standard/paseto-spec/blob/master/docs/Rationale-V3-V4.md#no-more-nonce-hashing-change
• Blake2b:
  • https://doc.libsodium.org/hashing/generic_hashing
  • https://datatracker.ietf.org/doc/html/rfc7693
  • https://monocypher.org/manual/hash
  • zcash/zcash#706 (comment)
• Ed25519:
  • https://doc.libsodium.org/public-key_cryptography/public-key_signatures
  • https://datatracker.ietf.org/doc/html/rfc8032
  • https://monocypher.org/manual/sign
• Argon2id:
  • https://www.password-hashing.net/
  • https://doc.libsodium.org/password_hashing