harmony 鸿蒙Randomly Generating an Asymmetric Key Pair (C/C++)

2025-06-12
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Randomly Generating an Asymmetric Key Pair (C/C++)

This topic uses RSA and SM2 as an example to describe how to generate an asymmetric key pair (OH_CryptoKeyPair) and obtain the binary data.

The OH_CryptoKeyPair object created can be used for subsequent encryption and decryption operations, and the binary data can be used for key storage and transfer.

Adding the Dynamic Library in the CMake Script

target_link_libraries(entry PUBLIC libohcrypto.so)

Randomly Generating an RSA Key Pair

For details about the algorithm specifications, see RSA.

Call OH_CryptoAsymKeyGenerator_Create with the string parameter ‘RSA1024|PRIMES_2’ to create an asymmetric key generator (OH_CryptoAsymKeyGenerator) object for a 1024-bit RSA key with two primes.
Call OH_CryptoAsymKeyGenerator_Generate to randomly generate an asymmetric key object (OH_CryptoKeyPair).
Call OH_CryptoPubKey_Encode to obtain the binary data of the public key.

#include "CryptoArchitectureKit/crypto_common.h"
#include "CryptoArchitectureKit/crypto_asym_key.h"

static OH_Crypto_ErrCode randomGenerateAsymKey()
{
    OH_CryptoAsymKeyGenerator *ctx = nullptr;
    OH_CryptoKeyPair *keyPair = nullptr;
    OH_Crypto_ErrCode ret;

    ret = OH_CryptoAsymKeyGenerator_Create("RSA1024|PRIMES_2", &ctx);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymKeyGenerator_Destroy(ctx);
        return ret;
    }


    ret = OH_CryptoAsymKeyGenerator_Generate(ctx, &keyPair);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymKeyGenerator_Destroy(ctx);
        OH_CryptoKeyPair_Destroy(keyPair);
        return ret;
    }

    OH_CryptoPubKey *pubKey = OH_CryptoKeyPair_GetPubKey(keyPair);
    Crypto_DataBlob retBlob = { .data = nullptr, .len = 0 };
    ret = OH_CryptoPubKey_Encode(pubKey, CRYPTO_PEM, "PKCS1", &retBlob);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymKeyGenerator_Destroy(ctx);
        OH_CryptoKeyPair_Destroy(keyPair);
        return ret;
    }

    OH_Crypto_FreeDataBlob(&retBlob);

    OH_CryptoAsymKeyGenerator_Destroy(ctx);
    OH_CryptoKeyPair_Destroy(keyPair);
    return ret;
}

Randomly Generating an SM2 Key Pair

For details about the algorithm specifications, see SM2.

Call OH_CryptoAsymKeyGenerator_Create with the string parameter ‘SM2_256’ to create an asymmetric key generator (OH_CryptoAsymKeyGenerator) object for a 256-bit SM2 key pair.
Call OH_CryptoAsymKeyGenerator_Generate to randomly generate an asymmetric key object (OH_CryptoKeyPair).
Call OH_CryptoPubKey_Encode to obtain the binary data of the public key.

#include "CryptoArchitectureKit/crypto_common.h"
#include "CryptoArchitectureKit/crypto_asym_key.h"

static OH_Crypto_ErrCode randomGenerateSm2KeyPair()
{
    OH_CryptoAsymKeyGenerator *ctx = nullptr;
    OH_CryptoKeyPair *dupKeyPair = nullptr;
    OH_Crypto_ErrCode ret;

    ret = OH_CryptoAsymKeyGenerator_Create("SM2_256", &ctx);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymKeyGenerator_Destroy(ctx);
        return ret;
    }

    ret = OH_CryptoAsymKeyGenerator_Generate(ctx, &dupKeyPair);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymKeyGenerator_Destroy(ctx);
        OH_CryptoKeyPair_Destroy(dupKeyPair);
        return ret;
    }

    OH_CryptoPubKey *pubKey = OH_CryptoKeyPair_GetPubKey(dupKeyPair);
    Crypto_DataBlob retBlob = { .data = nullptr, .len = 0 };
    ret = OH_CryptoPubKey_Encode(pubKey, CRYPTO_DER, nullptr, &retBlob);
    if (ret != CRYPTO_SUCCESS) {
        OH_CryptoAsymKeyGenerator_Destroy(ctx);
        OH_CryptoKeyPair_Destroy(dupKeyPair);
        return ret;
    }

    OH_CryptoAsymKeyGenerator_Destroy(ctx);
    OH_CryptoKeyPair_Destroy(dupKeyPair);
    return ret;
}