Crypto++ 8.6 Free C++ class library of cryptographic schemes

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Poly1305TLS Class Reference

Poly1305-TLS message authentication code. More...

Inheritance diagram for Poly1305TLS:

## Additional Inherited Members
Public Member Functions inherited from MessageAuthenticationCodeFinal< Poly1305TLS_Base >
| MessageAuthenticationCodeFinal ()
| Construct a default MessageAuthenticationCodeFinal. More...
| MessageAuthenticationCodeFinal (const byte *key)
| Construct a BlockCipherFinal. More...
| MessageAuthenticationCodeFinal (const byte *key, size_t length)
| Construct a BlockCipherFinal. More...
Public Member Functions inherited from ClonableImpl< DERIVED, BASE >
Clonable * | Clone () const
| Create a copy of this object. More...

## Detailed Description

Poly1305-TLS message authentication code.

This is the IETF's variant of Bernstein's Poly1305 from RFC 8439. IETF Poly1305 is called Poly1305TLS in the Crypto++ library. It is _slightly_ different from the Bernstein implementation. Poly1305-TLS can be used for cipher suites `TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256`, `TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256`, and `TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256`.

The key is 32 bytes and a concatenation `key = {r,s}`, where `r` is additional key that gets clamped and `s` is the nonce. The key is clamped internally so there is no need to perform the operation before setting the key.

Each message must have a unique security context, which means the key must be changed after each message. It can be accomplished in one of two ways. First, you can create a new Poly1305 object with a new key each time its needed.

      SecByteBlock key(32);
      prng.GenerateBlock(key, key.size());

      Poly1305TLS poly1305(key, key.size());
      poly1305.Update(...);
      poly1305.Final(...);

Second, you can create a Poly1305 object, and use a new key for each message. The keys can be generated directly using a RandomNumberGenerator() derived class.

      SecByteBlock key(32);
      prng.GenerateBlock(key, key.size());

      // First message
      Poly1305TLS poly1305(key, key.size());
      poly1305.Update(...);
      poly1305.Final(...);

      // Second message
      prng.GenerateBlock(key, key.size());
      poly1305.SetKey(key, key.size());
      poly1305.Update(...);
      poly1305.Final(...);
      ...

Warning
  Each message must have a unique security context. The Poly1305-TLS class does not enforce a fresh key or nonce for each message.

Since
  Crypto++ 8.1

See also
  MessageAuthenticationCode(), RFC 8439, ChaCha20 and Poly1305 for IETF Protocols

Definition at line 237 of file poly1305.h.

The documentation for this class was generated from the following file:

- poly1305.h