Package cryptobyte contains types that help with parsing and constructing length-prefixed, binary messages, including ASN.1 DER.

Package curve25519 provides an implementation of scalar multiplication on the elliptic curve known as curve25519.

Package hkdf implements the HMAC-based Extract-and-Expand Key Derivation Function (HKDF) as defined in RFC 5869.

Package poly1305 implements Poly1305 one-time message authentication code as specified in https://cr.yp.to/mac/poly1305-20050329.pdf.