Documentation

Overview

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

    Poly1305 is a fast, one-time authentication function. It is infeasible for an attacker to generate an authenticator for a message without the key. However, a key must only be used for a single message. Authenticating two different messages with the same key allows an attacker to forge authenticators for other messages with the same key.

    Poly1305 was originally coupled with AES in order to make Poly1305-AES. AES was used with a fixed key in order to generate one-time keys from an nonce. However, in this package AES isn't used and the one-time key is specified directly.

    Index

    Constants

    View Source
    const TagSize = 16

      TagSize is the size, in bytes, of a poly1305 authenticator.

      Variables

      This section is empty.

      Functions

      func Sum

      func Sum(out *[16]byte, m []byte, key *[32]byte)

        Sum generates an authenticator for msg using a one-time key and puts the 16-byte result into out. Authenticating two different messages with the same key allows an attacker to forge messages at will.

        func Verify

        func Verify(mac *[16]byte, m []byte, key *[32]byte) bool

          Verify returns true if mac is a valid authenticator for m with the given key.

          Types

          type MAC

          type MAC struct {
          	// contains filtered or unexported fields
          }

            MAC is an io.Writer computing an authentication tag of the data written to it.

            MAC cannot be used like common hash.Hash implementations, because using a poly1305 key twice breaks its security. Therefore writing data to a running MAC after calling Sum or Verify causes it to panic.

            func New

            func New(key *[32]byte) *MAC

              New returns a new MAC computing an authentication tag of all data written to it with the given key. This allows writing the message progressively instead of passing it as a single slice. Common users should use the Sum function instead.

              The key must be unique for each message, as authenticating two different messages with the same key allows an attacker to forge messages at will.

              func (*MAC) Size

              func (h *MAC) Size() int

                Size returns the number of bytes Sum will return.

                func (*MAC) Sum

                func (h *MAC) Sum(b []byte) []byte

                  Sum computes the authenticator of all data written to the message authentication code.

                  func (*MAC) Verify

                  func (h *MAC) Verify(expected []byte) bool

                    Verify returns whether the authenticator of all data written to the message authentication code matches the expected value.

                    func (*MAC) Write

                    func (h *MAC) Write(p []byte) (n int, err error)

                      Write adds more data to the running message authentication code. It never returns an error.

                      It must not be called after the first call of Sum or Verify.

                      GOOS=linux, GOARCH=amd64