sntrup(3)

  NAME
sntrup - C API for the libntruprime implementation of the Streamlined NTRU Prime cryptosystem

  SYNOPSIS
Using libntruprime:

        #include <ntruprime.h>

Link with -lntruprime.

Key generation (for, e.g., sntrup1277):

        unsigned char pk[sntrup1277_PUBLICKEYBYTES];
        unsigned char sk[sntrup1277_SECRETKEYBYTES];

        sntrup1277_keypair(pk,sk);

Encapsulation (for, e.g., sntrup1277):

        unsigned char ct[sntrup1277_CIPHERTEXTBYTES];
        unsigned char k[sntrup1277_BYTES];
        const unsigned char pk[sntrup1277_PUBLICKEYBYTES];

        sntrup1277_enc(ct,k,pk);

Decapsulation (for, e.g., sntrup1277):

        unsigned char k[sntrup1277_BYTES];
        const unsigned char ct[sntrup1277_CIPHERTEXTBYTES];
        const unsigned char sk[sntrup1277_SECRETKEYBYTES];

        sntrup1277_dec(k,ct,sk);

  DESCRIPTION
libntruprime is an implementation of the Streamlined NTRU Prime (https://ntruprime.cr.yp.to) cryptosystem. The C API for libntruprime provides the following functions:

        sntrup{653,761,857,953,1013,1277}_keypair
        sntrup{653,761,857,953,1013,1277}_enc
        sntrup{653,761,857,953,1013,1277}_dec

All of these functions follow the SUPERCOP API for KEMs (https://bench.cr.yp.to/call-kem.html) except that

•   the function names are libntruprime-specific instead of crypto_kem_*,

•   message lengths are long long instead of unsigned long long, and

•   the functions return void instead of int.

The details below use sntrup1277 as an example.

  KEY GENERATION
The sntrup1277_keypair function randomly generates Alice’s secret key sk[0], sk[1], ..., sk[sntrup1277_SECRETKEYBYTES-1] and Alice’s corresponding public key pk[0], pk[1], ..., pk[sntrup1277_PUBLICKEYBYTES-1].

  ENCAPSULATION
The sntrup1277_enc function randomly generates a ciphertext ct[0], ct[1], ..., ct[sntrup1277_CIPHERTEXTBYTES-1] and the corresponding session key k[0], k[1], ..., k[sntrup1277_BYTES-1] given Alice’s public key pk[0], pk[1], ..., pk[sntrup1277_PUBLICKEYBYTES-1].

  DECAPSULATION
The sntrup1277_dec function, given Alice’s secret key sk[0], sk[1], ..., sk[sntrup1277_SECRETKEYBYTES-1], computes the session key k[0], k[1], ..., k[sntrup1277_BYTES-1] corresponding to a ciphertext ct[0], ct[1], ..., ct[sntrup1277_CIPHERTEXTBYTES-1] that was encapsulated to Alice.

  SEE ALSO
sntrup(1), randombytes(3)