libsodium1

//
// $ git clone https://github.com/jedisct1/libsodium
// $ cd libsodium
// $ mkdir mylib
// $ ./autogen.sh
// $ ./configure --prefix=`pwd`/mylib --disable-shared
// $ make
// $ make install
// $ cd mylib
// $ gcc -Iinclude -o tst test_chacha20.c -Llib -lsodium
// $ ./tst
//
#include <stdio.h>
#include <stdlib.h>

#include <sodium/crypto_stream_chacha20.h>
#include <sodium/crypto_aead_chacha20poly1305.h>
#include <sodium/randombytes.h>


#define MESSAGE "digital television"
#define MESSAGE_LEN (sizeof(MESSAGE) - 1)
#define ADDITIONAL_DATA "abcdef"
#define ADDITIONAL_DATA_LEN (sizeof(ADDITIONAL_DATA) - 1)


// https://download.libsodium.org/doc/secret-key_cryptography/original_chacha20-poly1305_construction.html
void func(void)
{
    unsigned char nonce[crypto_aead_chacha20poly1305_NPUBBYTES];
    unsigned char key[crypto_aead_chacha20poly1305_KEYBYTES];
    unsigned char ciphertext[MESSAGE_LEN + crypto_aead_chacha20poly1305_ABYTES];
    unsigned long long ciphertext_len;

    randombytes_buf(key, sizeof key);
    randombytes_buf(nonce, sizeof nonce);

    crypto_aead_chacha20poly1305_encrypt(ciphertext, &ciphertext_len,
                                         (unsigned char *)MESSAGE, MESSAGE_LEN,
                                         (unsigned char *)ADDITIONAL_DATA, ADDITIONAL_DATA_LEN,
                                         NULL, nonce, key);

    printf("enc= ");
    for (int lp = 0; lp < ciphertext_len; lp++) {
        printf("%02x", ciphertext[lp]);
    }
    printf("\n\n");

    unsigned char decrypted[MESSAGE_LEN];
    unsigned long long decrypted_len;
    if (crypto_aead_chacha20poly1305_decrypt(decrypted, &decrypted_len,
                                             NULL,
                                             ciphertext, ciphertext_len,
                                             (unsigned char *)ADDITIONAL_DATA,
                                             ADDITIONAL_DATA_LEN,
                                             nonce, key) != 0) {
        /* message forged! */
    }

    printf("dec= ");
    for (int lp = 0; lp < decrypted_len; lp++) {
        printf("%02x(%c) ", decrypted[lp], decrypted[lp]);
    }
    printf("\n\n");
}


int main(void)
{
    const uint8_t NONCE[] = {
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
    };
    const char STR[] = "abcdefghi";

    int ret;
    uint8_t out[8];
    unsigned long long outlen = sizeof(out);

    ret = crypto_stream_chacha20(out, outlen, NONCE, STR);
    printf("crypto_stream_chacha20: ret=%d\n", ret);
    for (int lp = 0; lp < sizeof(out); lp++) {
        printf("%02x", out[lp]);
    }
    printf("\n\n");

    ret = crypto_stream_chacha20_ietf(out, outlen, NONCE, STR);
    printf("crypto_stream_chacha20_ietf: ret=%d\n", ret);
    for (int lp = 0; lp < sizeof(out); lp++) {
        printf("%02x", out[lp]);
    }
    printf("\n\n");


    func();

    return 0;
}

サイズを小さくしたくてenable-minimalしたけど、意味が違う。。。
ので、消した。