Encryption and Decryption with a ChaCha20 Symmetric Key Pair (Poly1305) (C/C++)

The Crypto framework supports this algorithm since API version 22.

For details about the algorithm specifications, see ChaCha20.

Adding the Dynamic Library in the CMake Script

target_link_libraries(entry PUBLIC libohcrypto.so)

How to Develop

Creating an Object

Call OH_CryptoSymKeyGenerator_Create and OH_CryptoSymKeyGenerator_Generate to generate a symmetric key (OH_CryptoSymKey) with the key algorithm being ChaCha20.

For details about how to generate a ChaCha20 symmetric key, see the following example. To learn more, see Symmetric Key Generation and Conversion Specifications: ChaCha20 and Randomly Generating a Symmetric Key. There may be differences between the input parameters in the reference documents and those in the following example.

Encryption

Call OH_CryptoSymCipher_Create with the string parameter 'ChaCha20|Poly1305' to create a Cipher instance for encryption. The key type is ChaCha20, and the mode is Poly1305.
Call OH_CryptoSymCipherParams_Create to create a parameter object and call OH_CryptoSymCipherParams_SetParam to set encryption parameters.
Call OH_CryptoSymCipher_Init to initialize the Cipher instance. Specifically, set mode to CRYPTO_ENCRYPT_MODE, and specify the key for encryption (OH_CryptoSymKey) and the encryption parameter instance (OH_CryptoSymCipherParams) corresponding to the Poly1305 mode.
Call OH_CryptoSymCipher_Update to update data (in plaintext).
Call OH_CryptoSymCipher_Final to obtain the encrypted data.

NOTE

If data has been passed in by Cipher.update, pass in null in the data parameter of Cipher.doFinal.

The output of Cipher.doFinal may be null. To avoid exceptions, always check whether the result is null before accessing specific data.
Call OH_CryptoSymCipherParams_Create to create a Params instance, and call OH_CryptoSymCipherParams_SetParam to set authTag as the authentication information for decryption. In Poly1305 mode, extract the last 16 bytes from the encrypted data as the authentication information for initializing the Cipher instance in decryption.
Call OH_CryptoSymKeyGenerator_Destroy, OH_CryptoSymCipher_Destroy, and OH_CryptoSymCipherParams_Destroy to destroy the objects.

Decryption

Call OH_CryptoSymCipher_Create with the string parameter 'ChaCha20|Poly1305' to create a Cipher instance for decryption. The key type is ChaCha20, and the mode is Poly1305.
Call OH_CryptoSymCipher_Init to initialize the Cipher instance. Specifically, set mode to CRYPTO_DECRYPT_MODE, and specify the decryption key (OH_CryptoSymKey) and the decryption parameter instance (OH_CryptoSymCipherParams) corresponding to the Poly1305 mode.
Call OH_CryptoSymCipher_Update to update data (in ciphertext).
Call OH_CryptoSymCipher_Final to obtain the decrypted data.

#include "CryptoArchitectureKit/crypto_common.h"
#include "CryptoArchitectureKit/crypto_sym_cipher.h"
#include <string.h>

static OH_Crypto_ErrCode doTestChaCha20Poly1305()
{
    OH_CryptoSymKeyGenerator *genCtx = nullptr;
    OH_CryptoSymCipher *encCtx = nullptr;
    OH_CryptoSymCipher *decCtx = nullptr;
    OH_CryptoSymKey *keyCtx = nullptr;
    OH_CryptoSymCipherParams *params = nullptr;

    Crypto_DataBlob outUpdate = {.data = nullptr, .len = 0};
    Crypto_DataBlob decUpdate = {.data = nullptr, .len = 0};

    uint8_t aad[8] = {1, 2, 3, 4, 5, 6, 7, 8};
    uint8_t tag[16] = {0};
    uint8_t iv[16] = {1, 2, 4, 12, 3, 4, 2, 3, 3, 2, 0, 4, 2, 4, 12, 3}; // iv is generated from an array of secure random numbers.
    Crypto_DataBlob ivData = {.data = iv, .len = sizeof(iv)};
    Crypto_DataBlob aadData = {.data = aad, .len = sizeof(aad)};
    Crypto_DataBlob tagData = {.data = tag, .len = sizeof(tag)};
    Crypto_DataBlob tagOutPut = {.data = nullptr, .len = 0};
    char *plainText = const_cast<char *>("this is test!");
    Crypto_DataBlob msgBlob = {.data = (uint8_t *)(plainText), .len = strlen(plainText)};
    // Generate a symmetric key.
    OH_Crypto_ErrCode ret;
    ret = OH_CryptoSymKeyGenerator_Create("ChaCha20", &genCtx);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymKeyGenerator_Generate(genCtx, &keyCtx);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }

    // Set parameters.
    ret = OH_CryptoSymCipherParams_Create(&params);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymCipherParams_SetParam(params, CRYPTO_IV_DATABLOB, &ivData);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymCipherParams_SetParam(params, CRYPTO_AAD_DATABLOB, &aadData);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymCipherParams_SetParam(params, CRYPTO_TAG_DATABLOB, &tagData);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }

    // Encrypt data.
    ret = OH_CryptoSymCipher_Create("ChaCha20|Poly1305", &encCtx);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymCipher_Init(encCtx, CRYPTO_ENCRYPT_MODE, keyCtx, params);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymCipher_Update(encCtx, &msgBlob, &outUpdate);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymCipher_Final(encCtx, nullptr, &tagOutPut);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }

    // Decrypt data.
    ret = OH_CryptoSymCipher_Create("ChaCha20|Poly1305", &decCtx);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymCipherParams_SetParam(params, CRYPTO_TAG_DATABLOB, &tagOutPut);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymCipher_Init(decCtx, CRYPTO_DECRYPT_MODE, keyCtx, params);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }
    ret = OH_CryptoSymCipher_Final(decCtx, &outUpdate, &decUpdate);
    if (ret != CRYPTO_SUCCESS) {
        goto end;
    }

    // Release the instance.
end:
    OH_CryptoSymCipherParams_Destroy(params);
    OH_CryptoSymCipher_Destroy(encCtx);
    OH_CryptoSymCipher_Destroy(decCtx);
    OH_CryptoSymKeyGenerator_Destroy(genCtx);
    OH_CryptoSymKey_Destroy(keyCtx);
    OH_Crypto_FreeDataBlob(&outUpdate);
    OH_Crypto_FreeDataBlob(&decUpdate);
    OH_Crypto_FreeDataBlob(&tagOutPut);
    return ret;
}