test_signatures.c

#include <sodium.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(void)
{
    if (sodium_init() < 0) {
        printf("can't init libsodium");
        return 1;
    }

    char ed25519_private_hex[] = "28e9e1d48cb0e52e437080e4a180058d7a42a07abcd05ea2ec4e6122cded8f6a0d2a6b9fd1878fd76ab20caecab666916ac3cc772fc57f8fa6e8dc3227bb8497";
    char ed25519_public_hex[] = "8fbe438aab6c40dc2ebc839ba27530ca1bf23d4efd36958a3365406efe52ccd1";

    unsigned char ed25519_private[64];
    size_t ed25519_private_len; 
    sodium_hex2bin(ed25519_private, sizeof ed25519_private, ed25519_private_hex, strlen(ed25519_private_hex), NULL, &ed25519_private_len, NULL);

    unsigned char ed25519_public[32];
    size_t ed25519_public_len; 
    sodium_hex2bin(ed25519_public, sizeof ed25519_public, ed25519_public_hex, strlen(ed25519_public_hex), NULL, &ed25519_public_len, NULL);

    unsigned char message[] = "hello";
    unsigned char signed_message[crypto_sign_BYTES + 5];
    unsigned long long signed_message_len;

    crypto_sign(signed_message, &signed_message_len, message, 5, ed25519_private);

    unsigned char unsigned_message[5];
    unsigned long long unsigned_message_len;
    if (crypto_sign_open(unsigned_message, &unsigned_message_len,
                         signed_message, signed_message_len, ed25519_public) != 0) {
        printf("signature incorrect\n");
    }
    else {
        printf("signature correcte\n");
    }

    return 0;
}