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)