Demo: Encoding and Cryptography

Demonstrates Base64, SHA-1 compatibility use, and AES-256-CBC APIs that return actual output lengths.

1. Example Scope

The page mirrors the repository source, CMake target, and current API, with English comments for the relevant calls.

2. Build and Run

cmake --build build --target sttnet_crypto_encoding --parallel
./build/examples/sttnet_crypto_encoding

3. Validation

./build/examples/sttnet_crypto_encoding

Expected: Prints Base64 encoding and decoding, SHA-1 hex text, ciphertext length, and the recovered plaintext.

4. Complete Source

#include <sttnet.h>

#include <array>
#include <iostream>
#include <string>
#include <vector>

int main()
{
    using stt::data::CryptoUtil;
    using stt::data::EncodingUtil;

    const std::string message="STTNet utility demo";

    // Base64 is reversible encoding, not encryption. Invalid encoded input is
    // rejected with an empty result; empty input also produces an empty result.
    const std::string base64=EncodingUtil::base64_encode(message);
    std::cout << "base64: " << base64 << '\n';
    std::cout << "decoded: " << EncodingUtil::base64_decode(base64) << '\n';

    // SHA-1 remains useful for protocol compatibility such as RFC 6455.
    // SHA-1 is retained for compatibility and is not suitable for password storage, signatures, or new security designs.
    std::string sha1Hex;
    CryptoUtil::sha11(message,sha1Hex);
    std::cout << "sha1: " << sha1Hex << '\n';

    // AES-256-CBC requires a 32-byte key and a 16-byte IV. Fixed values keep
    // this demo reproducible only. Production IVs are unpredictable, and CBC
    // ciphertext also needs authentication (or an AEAD mode).
    const std::array<unsigned char,32> key={
        '0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f',
        '0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
    const std::array<unsigned char,16> iv={
        'a','b','c','d','e','f','0','1','2','3','4','5','6','7','8','9'};

    // Reserve room for PKCS#7 padding and read the actual output length returned
    // by the overload. Binary output length comes from the API rather than inference.
    std::vector<unsigned char> cipher(message.size()+EVP_MAX_BLOCK_LENGTH);
    std::size_t cipherLength=0;
    if(!CryptoUtil::encryptSymmetric(
           reinterpret_cast<const unsigned char*>(message.data()),message.size(),
           key.data(),iv.data(),cipher.data(),cipherLength))
        return 1;

    std::vector<unsigned char> plain(cipherLength);
    std::size_t plainLength=0;
    if(!CryptoUtil::decryptSymmetric(cipher.data(),cipherLength,key.data(),iv.data(),
                                     plain.data(),plainLength))
        return 2;

    std::cout << "cipher bytes: " << cipherLength << '\n';
    std::cout << "decrypted: "
              << std::string(reinterpret_cast<char*>(plain.data()),plainLength)
              << '\n';
    return 0;
}