69 lines
1.9 KiB
C
69 lines
1.9 KiB
C
/*
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* GraxRabble
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* example programs for libsodium.
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*/
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#include <sodium.h> /* library header */
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#include "utils.h" /* utility functions shared by examples */
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/*
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* This operation computes an authentication tag for a message and a
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* secret key, and provides a way to verify that a given tag is valid
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* for a given message and a key.
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*
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* The function computing the tag deterministic: the same (message,
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* key) tuple will always produce the same output.
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*
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* However, even if the message is public, knowing the key is
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* required in order to be able to compute a valid tag. Therefore,
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* the key should remain confidential. The tag, however, can be
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* public.
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*
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* A typical use case is:
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*
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* - A prepares a message, add an authentication tag, sends it to B
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* - A doesn't store the message
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* - Later on, B sends the message and the authentication tag to A
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* - A uses the authentication tag to verify that it created this message.
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*
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* This operation does not encrypt the message. It only computes and
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* verifies an authentication tag.
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*/
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static int
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auth(void)
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{
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unsigned char key[crypto_auth_KEYBYTES];
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unsigned char mac[crypto_auth_BYTES];
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unsigned char message[MAX_INPUT_LEN];
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size_t message_len;
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int ret;
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puts("Example: crypto_auth\n");
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prompt_input("a key", (char*)key, sizeof key, 0);
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message_len = prompt_input("a message", (char*)message, sizeof message, 1);
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printf("Generating %s authentication...\n", crypto_auth_primitive());
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crypto_auth(mac, message, message_len, key);
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printf("Authentication tag: ");
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print_hex(mac, sizeof mac);
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puts("Verifying authentication tag...");
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ret = crypto_auth_verify(mac, message, message_len, key);
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print_verification(ret);
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sodium_memzero(key, sizeof key); /* wipe sensitive data */
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return ret;
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}
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int
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main(void)
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{
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init();
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return auth() != 0;
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}
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