libsodium/demos/sign.c

98 lines
2.6 KiB
C

/*
* GraxRabble
* 05 May 2014
* Demo programs for libsodium.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sodium.h> /* library header */
#include "demo_utils.h" /* utility functions shared by demos */
/*
* Signs a message with secret key which will authenticate a message.
* Everybody else can use the public key to ensure that the message is both
* valid and untampered.
*
* Note that the signed message will have 16 bytes of signature prepended.
* Ensure that the signed buffer is at least crypto_sign_BYTES longer then
* the actual message.
*/
static int
sign(void)
{
unsigned char pk[crypto_sign_PUBLICKEYBYTES]; /* Bob public */
unsigned char sk[crypto_sign_SECRETKEYBYTES]; /* Bob secret */
unsigned char m[BUFFER_SIZE]; /* message */
unsigned char sm[BUFFER_SIZE + crypto_sign_BYTES]; /* signed message */
unsigned long long int mlen; /* message length */
unsigned long long int smlen; /* signed length */
int r;
puts("Example: crypto_sign\n");
puts("Generating keypair...");
crypto_sign_keypair(pk, sk); /* generate Bob's keys */
fputs("Public: ", stdout);
print_hex(pk, sizeof pk);
putc('\n', stdout);
fputs("Secret: ", stdout);
print_hex(sk, sizeof sk);
puts("\n");
/* read input */
mlen = prompt_input("Input your message > ",
(char*) m, sizeof m - crypto_sign_BYTES);
putc('\n', stdout);
puts("Notice the message has no prepended padding");
print_hex(m, mlen);
putchar('\n');
putchar('\n');
printf("Signing message with %s...\n", crypto_sign_primitive());
crypto_sign(sm, &smlen, m, mlen, sk);
puts("Notice the signed message has prepended signature");
print_hex(sm, smlen);
putchar('\n');
putchar('\n');
puts("Format: signature::message");
fputs("Signed: ", stdout);
print_hex(sm, crypto_sign_BYTES);
fputs("::", stdout);
puts((const char*) sm + crypto_sign_BYTES);
putc('\n', stdout);
puts("Validating message...");
r = crypto_sign_open(m, &mlen, sm, smlen, pk);
print_verification(r);
if (r == 0) printf("Message: %s\n\n", m);
sodium_memzero(pk, sizeof pk); /* wipe sensitive data */
sodium_memzero(sk, sizeof sk);
sodium_memzero(m, sizeof m);
sodium_memzero(sm, sizeof sm);
return r;
}
int
main(int argc, char **argv)
{
int r;
sodium_init();
printf("Using LibSodium %s\n", sodium_version_string());
r = (0 == sign() ? EXIT_SUCCESS : EXIT_FAILURE);
exit(r);
}