bool
prompt_yesno(const char *prompt)
{
char prompt2[SIZEOF_STR];
if (!string_format(prompt2, "%s [Yy/Nn]", prompt))
return FALSE;
return !!prompt_input(prompt2, prompt_yesno_handler, NULL);
}
char *
read_prompt_incremental(const char *prompt, bool edit_mode, input_handler handler, void *data)
{
static struct incremental_input incremental = { { read_prompt_handler } };
incremental.input.data = data;
incremental.handler = handler;
incremental.edit_mode = edit_mode;
return prompt_input(prompt, (struct input *) &incremental);
}
/*
* Using public-key authenticated encryption, Bob can encrypt a
* confidential message specifically for Alice, using Alice's public
* key.
*
* Using Bob's public key, Alice can verify that the encrypted
* message was actually created by Bob and was not tampered with,
* before eventually decrypting it.
*
* Alice only needs Bob's public key, the nonce and the ciphertext.
* Bob should never ever share his secret key, even with Alice.
*
* And in order to send messages to Alice, Bob only needs Alice's
* public key. Alice should never ever share her secret key either,
* even with Bob.
*
* Alice can reply to Bob using the same system, without having to
* generate a distinct key pair.
*
* The nonce doesn't have to be confidential, but it should be used
* with just one invokation of crypto_box_open_easy() for a
* particular pair of public and secret keys.
*
* One easy way to generate a nonce is to use randombytes_buf(),
* considering the size of nonces the risk of any random collisions
* is negligible. For some applications, if you wish to use nonces to
* detect missing messages or to ignore replayed messages, it is also
* ok to use a simple incrementing counter as a nonce.
*
* When doing so you must ensure that the same value can never be
* re-used (for example you may have multiple threads or even hosts
* generating messages using the same key pairs).
*
* This system provides mutual authentication. However, a typical use
* case is to secure communications between a server, whose public
* key is known in advance, and clients connecting anonymously.
*/
static int
box_detached(void)
{
unsigned char bob_pk[crypto_box_PUBLICKEYBYTES]; /* Bob's public key */
unsigned char bob_sk[crypto_box_SECRETKEYBYTES]; /* Bob's secret key */
unsigned char alice_pk[crypto_box_PUBLICKEYBYTES]; /* Alice's public key */
unsigned char alice_sk[crypto_box_SECRETKEYBYTES]; /* Alice's secret key */
unsigned char nonce[crypto_box_NONCEBYTES];
unsigned char message[MAX_INPUT_LEN];
unsigned char mac[crypto_box_MACBYTES];
unsigned char ciphertext[MAX_INPUT_LEN];
size_t message_len;
int ret;
puts("Example: crypto_box_detached\n");
puts("Generating keypairs...\n");
crypto_box_keypair(bob_pk, bob_sk); /* generate Bob's keys */
crypto_box_keypair(alice_pk, alice_sk); /* generate Alice's keys */
puts("Bob");
printf("Public key: ");
print_hex(bob_pk, sizeof bob_pk);
printf("Secret key: ");
print_hex(bob_sk, sizeof bob_sk);
puts("Alice");
printf("Public key: ");
print_hex(alice_pk, sizeof alice_pk);
printf("Secret key: ");
print_hex(alice_sk, sizeof alice_sk);
/* nonce must be unique per (key, message) - it can be public and deterministic */
puts("Generating nonce...");
randombytes_buf(nonce, sizeof nonce);
printf("Nonce: ");
print_hex(nonce, sizeof nonce);
/* read input */
message_len = prompt_input("a message", (char*)message, sizeof message, 1);
print_hex(message, message_len);
/* encrypt and authenticate the message */
printf("Encrypting and authenticating with %s\n\n", crypto_box_primitive());
crypto_box_detached(ciphertext, mac, message, message_len, nonce,
alice_pk, bob_sk);
/* send the nonce, the MAC and the ciphertext */
puts("Bob sends the nonce, the MAC and the ciphertext...\n");
printf("Nonce: ");
print_hex(nonce, sizeof nonce);
printf("MAC: ");
print_hex(mac, sizeof mac);
printf("Ciphertext: ");
print_hex(ciphertext, message_len);
/* decrypt the message */
puts("Alice verifies the MAC and decrypts the ciphertext...");
ret = crypto_box_open_detached(message, ciphertext, mac, message_len, nonce,
bob_pk, alice_sk);
print_hex(message, message_len);
print_verification(ret);
if (ret == 0) {
printf("Plaintext: ");
fwrite(message, 1U, message_len, stdout);
putchar('\n');
}
sodium_memzero(bob_sk, sizeof bob_sk); /* wipe sensitive data */
sodium_memzero(alice_sk, sizeof alice_sk);
sodium_memzero(message, sizeof message);
sodium_memzero(ciphertext, sizeof ciphertext);
return ret;
}
char *
read_prompt(const char *prompt)
{
return prompt_input(prompt, read_prompt_handler, NULL);
}
