poly1305.h File Reference

Poly1305 one-time authenticator (D. J. Bernstein; RFC 8439 Section 2.5). More...

#include <stddef.h>
#include <stdint.h>

Go to the source code of this file.

Macros
#define	PC_POLY1305_KEY_LEN   32
#define	PC_POLY1305_TAG_LEN   16

Functions
void	pc_poly1305 (uint8_t tag[PC_POLY1305_TAG_LEN], const uint8_t *msg, size_t len, const uint8_t key[PC_POLY1305_KEY_LEN])
	Compute the 16-byte Poly1305 tag over msg under the 32-byte one-time key.

Detailed Description

Poly1305 one-time authenticator (D. J. Bernstein; RFC 8439 Section 2.5).

A one-time MAC over a message under a 32-byte key (r || s). Used by the chach.nosp@m.a20-.nosp@m.poly1.nosp@m.305@.nosp@m.opens.nosp@m.sh.c.nosp@m.om cipher, where the key is the first 32 bytes of the ChaCha20 block-0 keystream for the packet. 130-bit modular arithmetic in 5 x 26-bit limbs (poly1305-donna layout). Pure, no heap; the caller must use each key exactly once.

Author

Douglas Quigg (dstroy0)

Date

2026

Definition in file poly1305.h.

Macro Definition Documentation

PC_POLY1305_KEY_LEN

#define PC_POLY1305_KEY_LEN   32

Definition at line 23 of file poly1305.h.

PC_POLY1305_TAG_LEN

#define PC_POLY1305_TAG_LEN   16

Definition at line 24 of file poly1305.h.

Function Documentation

pc_poly1305()

void pc_poly1305	(	uint8_t	tag[PC_POLY1305_TAG_LEN],
		const uint8_t *	msg,
		size_t	len,
		const uint8_t	key[PC_POLY1305_KEY_LEN]
	)

Compute the 16-byte Poly1305 tag over msg under the 32-byte one-time key.

Definition at line 97 of file poly1305.cpp.

References pc_span::buf, pc_span_ok(), and SecureBorrow::span().

Referenced by pc_chachapoly_decrypt(), and pc_chachapoly_encrypt().