sha256生成RSA密匙对的C++实现

以下是基于OpenSSL库的C++代码实现：

#include <openssl/rsa.h>
#include <openssl/sha.h>
#include <openssl/bio.h>
#include <openssl/pem.h>

void generateRSAKeyPair(char* publicKey, char* privateKey) {
    RSA *rsa = RSA_new();
    BIGNUM *bn = BN_new();
    SHA256_CTX sha256;
    unsigned char hash[SHA256_DIGEST_LENGTH];
    char hexHash[SHA256_DIGEST_LENGTH * 2 + 1];
    BIO *bio = NULL;
    int ret;

    // 生成RSA密钥对
    BN_set_word(bn, RSA_F4);
    RSA_generate_key_ex(rsa, 2048, bn, NULL);
    BN_free(bn);

    // 生成公钥PEM文件
    bio = BIO_new(BIO_s_mem());
    ret = PEM_write_bio_RSAPublicKey(bio, rsa);
    if (ret != 1) {
        printf("Error: Failed to write public key!\n");
        RSA_free(rsa);
        BIO_free(bio);
        return;
    }
    ret = BIO_flush(bio);
    if (ret != 1) {
        printf("Error: Failed to flush BIO!\n");
        RSA_free(rsa);
        BIO_free(bio);
        return;
    }
    ret = BIO_get_mem_data(bio, &publicKey);
    if (ret <= 0) {
        printf("Error: Failed to get public key data from BIO!\n");
        RSA_free(rsa);
        BIO_free(bio);
        return;
    }
    publicKey[ret] = '\0';
    BIO_free(bio);

    // 生成私钥PEM文件
    bio = BIO_new(BIO_s_mem());
    ret = PEM_write_bio_RSAPrivateKey(bio, rsa, NULL, NULL, 0, NULL, NULL);
    if (ret != 1) {
        printf("Error: Failed to write private key!\n");
        RSA_free(rsa);
        BIO_free(bio);
        return;
    }
    ret = BIO_flush(bio);
    if (ret != 1) {
        printf("Error: Failed to flush BIO!\n");
        RSA_free(rsa);
        BIO_free(bio);
        return;
    }
    ret = BIO_get_mem_data(bio, &privateKey);
    if (ret <= 0) {
        printf("Error: Failed to get private key data from BIO!\n");
        RSA_free(rsa);
        BIO_free(bio);
        return;
    }
    privateKey[ret] = '\0';
    BIO_free(bio);

    // 计算公钥SHA256哈希值
    SHA256_Init(&sha256);
    ret = i2d_RSAPublicKey(rsa, NULL);
    if (ret <= 0) {
        printf("Error: Failed to get public key data length!\n");
        RSA_free(rsa);
        return;
    }
    unsigned char *publicKeyData = (unsigned char *)malloc(ret);
    ret = i2d_RSAPublicKey(rsa, &publicKeyData);
    if (ret <= 0) {
        printf("Error: Failed to get public key data!\n");
        RSA_free(rsa);
        free(publicKeyData);
        return;
    }
    SHA256_Update(&sha256, publicKeyData, ret);
    free(publicKeyData);
    SHA256_Final(hash, &sha256);

    // 将SHA256哈希值转换为十六进制字符串
    for (int i = 0; i < SHA256_DIGEST_LENGTH; i++) {
        sprintf(hexHash + i * 2, "%02x", hash[i]);
    }
    hexHash[SHA256_DIGEST_LENGTH * 2] = '\0';

    printf("Public Key:\n%s\n", publicKey);
    printf("Private Key:\n%s\n", privateKey);
    printf("Public Key SHA256 Hash:\n%s\n", hexHash);

    RSA_free(rsa);
}

其中，`generateRSAKeyPair`函数接受两个`char`类型的指针参数，用于返回生成的公钥和私钥PEM文件内容。该函数实现了以下操作：

1. 生成2048位RSA密钥对；
2. 将公钥PEM文件内容写入内存`BIO`中，并获取其数据；
3. 将私钥PEM文件内容写入内存`BIO`中，并获取其数据；
4. 计算公钥的SHA256哈希值，并将其转换为十六进制字符串；
5. 打印公钥、私钥和SHA256哈希值。

需要注意的是，该实现使用了OpenSSL库中的函数，因此需要在编译时链接OpenSSL库。