RSA作为最主流的加解密与验签算法，iOS当然少不了

签名

unsigned char *rsaPKCS1SignData(const unsigned char *src,int src_len,unsigned char*pri_key,int pri_key_len, int *dst_len)
{
        unsigned char *pri_pem =  formatPem(pri_key, PEM_FORMAT_PRIVATEKEY);
        BIO *bio_private = NULL;
        RSA *rsa_private = NULL;
        bio_private = BIO_new(BIO_s_mem());
        BIO_write(bio_private, pri_pem, strlen((const char *)pri_pem));
        unsigned char pwd[] = "";
        rsa_private = PEM_read_bio_RSAPrivateKey(bio_private, NULL, (pem_password_cb *)pwd,NULL);
        EVP_PKEY *key = EVP_PKEY_new();
        int err = EVP_PKEY_assign_RSA(key,rsa_private);
        int size=0;
        if (err) {
            size = EVP_PKEY_size(key);
        }
        EVP_MD_CTX *ctx = EVP_MD_CTX_create();
        EVP_MD_CTX_init(ctx);
        EVP_SignInit_ex(ctx,EVP_sha1() , NULL);
        EVP_SignUpdate(ctx, src,src_len);
        unsigned char *md=(unsigned char *)malloc(size);
        unsigned int len = 0;
        EVP_SignFinal(ctx, md, &len, key);
        *dst_len = len;
        EVP_PKEY_free(key);
        EVP_MD_CTX_cleanup(ctx);
        return md;
}



验签

bool rsaVerify(const unsigned char *src,int src_len,unsigned char *sig,unsigned int sigl_len,unsigned char *pub_key,int pub_key_len)
{
        unsigned char *pub_pem =  formatPem(pub_key, PEM_FORMAT_PUBKEY);
        BIO *bio_public = NULL;
        bio_public = BIO_new(BIO_s_mem());
        BIO_write(bio_public, pub_pem, strlen((const char *)pub_pem));
        EVP_PKEY *key=NULL;
        PEM_read_bio_PUBKEY(bio_public, &key, NULL, NULL);
        int size=0;
        if (key) {
            size = EVP_PKEY_size(key);
        }
        EVP_MD_CTX *ctx = EVP_MD_CTX_create();
        EVP_MD_CTX_init(ctx);
        EVP_VerifyInit_ex(ctx, EVP_sha1(), NULL);
        EVP_VerifyUpdate(ctx, src,src_len);
        int suc = EVP_VerifyFinal(ctx, sig, sigl_len, key);
        EVP_PKEY_free(key);
        EVP_MD_CTX_cleanup(ctx);
        if (suc == 1) {
            return true;
        }
        else
            return false;
}