基于Gmssl的SM2加解密算法Demo

基于Gmssl的SM2加解密算法Demo

存储小咖 2018-12-28 18:38:11 4739 收藏 5
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GmSSL介绍
Gmssl介绍:http://gmssl.org/
当然本文也是参考 http://gmssl.org/
其中SM2为非对称算法

SM2密钥生成

pair<string, string> GenKey(void)
{
EC_KEY *keypair = NULL;
EC_GROUP *group1 = NULL;

keypair = EC_KEY_new();
if(!keypair) {
cout << "Failed to Gen Key" << endl;
exit(1);
}

group1 = EC_GROUP_new_by_curve_name(NID_sm2p256v1);

if(group1 == NULL){
cout << "Failed to Gen Key" << endl;
exit(1);
}

int ret1 = EC_KEY_set_group(keypair, group1);
if(ret1 != 1){
cout << "Failed to Gen Key" << endl;
exit(1);
}

int ret2 = EC_KEY_generate_key(keypair);
if(ret2 != 1){
cout << "Failed to Gen Key" << endl;
exit(1);
}

size_t pri_len;
size_t pub_len;
char *pri_key = NULL;
char *pub_key = NULL;

BIO *pri = BIO_new(BIO_s_mem());
BIO *pub = BIO_new(BIO_s_mem());

PEM_write_bio_ECPrivateKey(pri, keypair, NULL, NULL, 0, NULL, NULL);
PEM_write_bio_EC_PUBKEY(pub, keypair);

pri_len = BIO_pending(pri);
pub_len = BIO_pending(pub);

pri_key = new char[pri_len + 1];
pub_key = new char[pub_len + 1];

BIO_read(pri, pri_key, pri_len);
BIO_read(pub, pub_key, pub_len);

pri_key[pri_len] = '\0';
pub_key[pub_len] = '\0';

string public_key = pub_key;
string private_key = pri_key;

EC_KEY_free(keypair);
BIO_free_all(pub);
BIO_free_all(pri);
delete [] pri_key;
delete [] pub_key;

return std::pair<string, string>(public_key, private_key);
}
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已字符串形式的返回,主要考虑我们在实际运用中,可能需要传递密钥信息,所以生成的SM2公钥和私钥以字符串形式返回。

从字符串类型的密钥中生成出来EC_KEY对象
EC_KEY* CreateEC(unsigned char* key, int is_public)
{
EC_KEY *ec_key = NULL;
BIO *keybio = NULL;
keybio = BIO_new_mem_buf(key, -1);

if (keybio==NULL) {
cout << "Failed to Get Key" << endl;
exit(1);
}

if(is_public) {
ec_key = PEM_read_bio_EC_PUBKEY(keybio, NULL, NULL, NULL);
}
else {
ec_key = PEM_read_bio_ECPrivateKey(keybio, NULL, NULL, NULL);
}

if(ec_key == NULL) {
cout << "Failed to Get Key" << endl;
exit(1);
}

return ec_key;
}
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SM2公钥加密
string Encrypt(const string& public_key, const string& plain_text)
{
unsigned char encrypted[1024] = {};

EC_KEY *rsa = CreateEC((unsigned char*)public_key.c_str(), 1);
size_t encrypted_length = 1024;
int ret = SM2_encrypt_with_recommended((unsigned char*)plain_text.c_str(), plain_text.length(),
(unsigned char*)encrypted,&encrypted_length, rsa);

if (ret == 0) {
cout << "Failed to Encrypt" << endl;
exit(1);
}

string enc_text((char*)encrypted, encrypted_length);
return enc_text;
}
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这里使用的加密函数为SM2_encrypt_with_recommended

SM2私钥解密
string Decrypt(const string& private_key, const string& enc_text)
{
unsigned char decrypted[1024] = {};

EC_KEY * key1 = CreateEC((unsigned char*)private_key.c_str(), 0);

size_t decrypted_length = 0;
int ret = SM2_decrypt_with_recommended((unsigned char*)enc_text.c_str(), enc_text.length(), decrypted, &decrypted_length, key1);

if (ret == 0) {
cout << "Failed to Decrypt" << endl;
exit(1);
}

string plain_text((char*)decrypted, decrypted_length);
return plain_text;
}
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这里使用的解密函数为SM2_decrypt_with_recommended

测试用例代码
下载:https://download.csdn.net/download/liulangaliulang/10884044
用例运行结果:

————————————————
版权声明:本文为CSDN博主「存储小咖」的原创文章,遵循CC 4.0 BY-SA版权协议,转载请附上原文出处链接及本声明。
原文链接:https://blog.csdn.net/liulangaliulang/article/details/85329878

SM2加解密算法(基于GMSSL的C代码实现)

 

一、椭圆曲线密码算法

  • 椭圆曲线:是一类二元多项式方程,它的解构成一个椭圆曲线。

  • 椭圆曲线参数:定义一条唯一的椭圆曲线。介绍其中两个参数G(基点)和n(阶)。G点(xG, yG)是椭圆曲线上的基点, 有限域椭圆曲线上所有其他的点都可以通过G点的倍乘运算计算得到,即P=[d]G, d也是属于有限域,d的最大值为素数n。

  • 有限域上的椭圆曲线:椭圆曲线上的解不是连续的,而是离散的,解的值满足有限域的限制。有限域有两种,Fp和F2m。

  • E(Fq):Fq上椭圆曲线E 的所有有理点(包括无穷远点O)组成的集合。

  • Fp:一个素整数的集合,最大值为P-1,集合中的值都是素数,里面元素满足以下模运算: a+b=(a+b) mod p 和 ab=(ab) mod p。

  • SM2:有限域Fp上的一条椭圆曲线,其椭圆曲线参数是固定值。

  • 公私钥:P=[d]G,G是已知的,大数d为私钥,点P(XP, YP)为公钥。

  • SM2推荐使用素数域256位椭圆曲线:
    -->EC_GROUP_new_by_curve_name(NID_sm2p256v1)

//可以得出固定参数
//Sm2 中指定的参数 确定下y2 = x3 + ax + b 曲线
#define _P  "FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFF"
#define _a  "FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFC"
#define _b  "28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E93"
#define _n  "FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFF7203DF6B21C6052B53BBF40939D54123"
#define _Gx "32C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7"
#define _Gy "BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0"
  • OpenSSL部分涉及代码
//初始化一个空算法组
EC_GROUP *group = EC_GROUP_new(EC_GFp_mont_method());
//初始化一个推荐椭圆曲线的算法组
EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_sm2p256v1);
//上下文
BN_CTX *ctx = BN_CTX_new();
//创建EC_KEY,使用推荐椭圆曲线
EC_KEY *ec_key  = EC_KEY_new_by_curve_name(NID_sm2p256v1)
//生成公钥私钥
EC_KEY_generate_key(ec_key);
//设置私钥
EC_KEY_set_private_key(ec_key, d);
//设置公钥
EC_KEY_set_public_key(ec_key, P);
//通过ec_key获取算法组
EC_GROUP *ec_group = EC_KEY_get0_group(ec_key);
//获取基点G
EC_POINT * G = EC_GROUP_get0_generator(ec_group);
//大数初始化
BIGNUM *rand = BN_new();
//EC_POINT初始化
EC_POINT *P = EC_POINT_new(ec_group);
//获取坐标点p的x,y值
EC_POINT_get_affine_coordinates_GFp(ec_group,p,x,y,ctx);
//Gets the order of a EC_GROUP -- n阶 对应上面固定参数的_n
EC_GROUP_get_order(ec_group, order, ctx);
//随机数生成
do {
     BN_rand_range(rand,order);
} while (BN_is_zero(rand));
//大数转二进制
int len = BN_bn2bin(bn, outChar);
//获取坐标点p转大数bn
EC_POINT_point2bn(ec_group, p, POINT_CONVERSION_COMPRESSED, bn, ctx);
//点的乘积  lP = P * rand
EC_POINT_mul(ec_group, lP, NULL, P, rand, ctx);
//验证点C1是否在椭圆曲线上
EC_POINT_is_on_curve(ec_group, c1, ctx);

马上开始

二、SM2加密算法(手动实现和使用GMSSL库实现)

PS:加解密中,加密时椭圆曲线点C1转换方式必须和解密时椭圆曲线点C1转换方式一致,否则无法解出C1。

1、手动实现

  • 流程


     
    image.png
  • 算法:

1、产生随机数k, k的值从1到n-1;

    BIGNUM *n,*k;
    n = BN_new();
    k = BN_new();
    EC_GROUP_get_order(ec_group, n, ctx);
    do {
        BN_rand_range(k,n);
    } while (BN_is_zero(k));

2、计算椭圆曲线点C1=[k]G=(x1,y1), 将C1使用EC_POINT_point2oct转换成比特串;

    //获取基点G
    const EC_POINT *G = EC_GROUP_get0_generator(ec_group);
    EC_POINT *c1 = NULL;
    c1 = EC_POINT_new(ec_group);
    unsigned char c1bin[65];
    unsigned long c1binlen = 65;
    EC_POINT_mul(ec_group, c1, NULL, G, k, ctx);
    EC_POINT_point2oct(ec_group, c1, POINT_CONVERSION_UNCOMPRESSED, c1bin, c1binlen, ctx);

3、 验证公钥PB, 计算S=[h] PB,如果S是无穷远点,出错退出;

    EC_POINT_is_on_curve(ec_group, PB, ctx);
    EC_POINT_is_at_infinity(ec_group, s);

4、计算(x2,y2)=[k] PB

    EC_POINT *tempPoint = EC_POINT_new(ec_group);
    BIGNUM *x2 = BN_new();
    BIGNUM *y2 = BN_new();
    EC_POINT_mul(ec_group, tempPoint, NULL, pb, k, ctx);
    EC_POINT_get_affine_coordinates_GFp(ec_group,
                                        tempPoint, x2, y2, ctx);

5、计算t=KDF(x2||y2, klen), KDF是密钥派生函数,klen是明文长度。

    unsigned char x2y2[64] = {0};
    unsigned long x2y2len = 0;
    //x2||y2
    x2y2len += BN_bn2bin(x2, x2y2);
    x2y2len += BN_bn2bin(y2, &x2y2[32]);
    unsigned char t[klen];
    unsigned long tlen = klen;
    kdf(EVP_sm3(), x2y2, sizeof(x2y2), t, &tlen);

//kdf方法
void *kdf(const EVP_MD *md, const void *in, size_t inlen,
              void *out, size_t *outlen)
{
    EVP_MD_CTX ctx;
    uint32_t counter = 1;
    uint32_t counter_be;
    unsigned char dgst[EVP_MAX_MD_SIZE];
    unsigned int dgstlen;
    unsigned char *pout = out;
    size_t rlen = *outlen;
    size_t len;
    
    EVP_MD_CTX_init(&ctx);
    
    while (rlen > 0) {
        counter_be = cpu_to_be32(counter);
        counter++;
        
        EVP_DigestInit(&ctx, md);
        EVP_DigestUpdate(&ctx, in, inlen);
        EVP_DigestUpdate(&ctx, &counter_be, sizeof(counter_be));
        EVP_DigestFinal(&ctx, dgst, &dgstlen);
        
        len = dgstlen <= rlen ? dgstlen : rlen;
        memcpy(pout, dgst, len);
        rlen -= len;
        pout += len;
    }
    
    EVP_MD_CTX_cleanup(&ctx);
    return out;
}

6、计算C2=M^t (此处^为异或)

    unsigned char c2[tlen];
    unsigned long c2len = 0;
    for (int i = 0; i < tlen; i ++) {
        c2[i] = M[i] ^ t[i];
        c2len++;
    }

7、 计算C3=Hash(x2||M||y2)

    unsigned char c3[32];
    unsigned long c3len = 32;
    unsigned char tempC3[x2y2len+klen];
    BN_bn2bin(x2, tempC3);
    BN_bn2bin(y2, &tempC3[32+klen]);
    memcpy(&tempC3[32], M, klen);
    sm3(tempC3, x2y2len+klen, c3);

8、 输出密文C=C1||C3||C2。

    unsigned char c[c1binlen + c2len + c3len];
    unsigned long clen = c1binlen + c2len + c3len;
    memcpy(c, c1bin, c1binlen);
    memcpy(&c[c1binlen], c3, c3len);
    memcpy(&c[c1binlen+c3len], c2, c2len);

注:密文分为C1,C2,C3,三部分,C1长度是65字节(具体根据转换方式),C2是明文的长度,C3是32字节(Hash使用sm3)。
注:C1 || C2 || C3 的意思就是拼在一起,而不是做什么或运算

  • 根据国密推荐的SM2椭圆曲线公钥密码算法,首先产生随机数计算出曲线点C1,2个32byte的BIGNUM大数,即为SM2加密结果的第1部分(C1)。第2部分则是真正的密文,是对明文的加密结果,长度和明文一样(C2)。第3部分是杂凑值,用来效验数据(C3)。按国密推荐的256位椭圆曲线,明文加密结果比原长度会大97byte(C1使用EC_POINT_point2oct转换)。
  • 注:通过密钥派生函数计算,才能进行第6步的按位异或计算。

2、使用GMSSL库实现

  • 基于GmSSL 1.2.2 (OpenSSL 1.0.2d)
/**
 修复BN_bn2bin函数结果不为32的情况(高位补0)
 @param sourceBn 源BIGNUM
 @param out 输出
 @return 返回长度
 */
int fixBn2Bin(BIGNUM *sourceBn,unsigned char *out){
    unsigned char tempBin[32] = {0};
    int tempLen = BN_bn2bin(sourceBn, tempBin);
    if (tempLen != 32) {
        memset(out, 0, 32 - tempLen);
    }
    memcpy(&out[32-tempLen], tempBin, tempLen);
    return 32;
}
#define RV_OK  0x00000000  //success
#define RV_EncErr  0x01000010  //encrypt error
/**
 SM2加密 使用国密GMSSL库

 @param P 公钥
 @param encryptData 需要加密的数据
 @param outData 输出加密后的数据
 @param outDataLen 输出加密后的数据长度
 @return 0成功/其它失败
 */
int sm2EncryptByGMSSL(EC_POINT *P,unsigned char *encryptData,unsigned long encryptDataLen,unsigned char *outData,unsigned long *outDataLen){
    int resultCode = RV_OK;
    //变量
    EC_KEY *ec_key = EC_KEY_new_by_curve_name(NID_sm2p256v1);
    EC_KEY_set_public_key(ec_key, P);
    const EC_GROUP *ec_group = EC_KEY_get0_group(ec_key);

    BN_CTX *ctx = BN_CTX_new();
    SM2_CIPHERTEXT_VALUE *cv = NULL;
    SM2_ENC_PARAMS params;

    //c1
    BIGNUM *x = NULL;
    BIGNUM *y = NULL;
    unsigned char *c1Buf = NULL;
    unsigned long c1Len = 0;
    
    //开始加密(使用GMSSL的方法)
    SM2_ENC_PARAMS_init_with_recommended(&params);
    if (!(cv = SM2_do_encrypt(&params, encryptData, encryptDataLen, ec_key))) {
        resultCode = RV_EncErr;
        goto end;
    }
    OPENSSL_assert(cv);
    //C1
    //确定c1所需空间
    if (!(c1Len = EC_POINT_point2oct(ec_group, cv->ephem_point,
                                     params.point_form, NULL, 0, ctx))) {
        resultCode = RV_EncErr;
        goto end;
    }
    //创建c1所需空间
    c1Buf = malloc(c1Len);
    if (!(c1Len = EC_POINT_point2oct(ec_group, cv->ephem_point,
                                     params.point_form, c1Buf, c1Len, ctx))) {
        resultCode = RV_EncErr;
        goto end;
    }
    memcpy(outData, c1Buf, c1Len);
    //获取C1方法二
//    unsigned char c1Bin[64] = {0};
//    x = BN_new();
//    y = BN_new();
//    EC_POINT_get_affine_coordinates_GFp(ec_group,cv->ephem_point, x, y, ctx);
//
//    fixBn2BinLen(x,c1Bin);
//    fixBn2BinLen(y,&c1Bin[32]);
//    //拼接C1
//    memcpy(outData, c1Bin, 64);
    
    //后续拼接
    //拼接C3
    memcpy(outData+c1Len, cv -> mactag, cv->mactag_size);
    //拼接C2
    memcpy(outData+c1Len+cv->mactag_size, cv ->ciphertext, cv->ciphertext_size);
    *outDataLen = c1Len + cv->mactag_size + cv->ciphertext_size;
    
end:
    EC_KEY_free(ec_key);
    BN_CTX_free(ctx);
    if(cv != NULL) SM2_CIPHERTEXT_VALUE_free(cv);
    if(x != NULL) BN_free(x);
    if(y != NULL) BN_free(y);
    if (c1Buf != NULL) {
        free(c1Buf);
    }
    return resultCode;
}
  • 基于GmSSL 2.5.4 - OpenSSL 1.1.0d 3 Sep 2019
/**
 使用gmssl SM2加密
 
 @param inData 需要加密的数据
 @param inDataLen 需要加密的数据长度
 @param pubKey 公钥(point2oct)
 @param pubKeyLen 公钥长度
 @param encryptData 加密后的数据
 @return 0:成功/非0:失败
 */
 int sm2EncryptByGMSSL(
                       unsigned char *inData,
                       unsigned long inDataLen,
                       unsigned char *pubKey,
                       unsigned long pubKeyLen,
                       SM2CiphertextValue **encryptData)
{
    int resultCode = RV_OK;
    //公钥
    EC_KEY *ec_key = NULL;
    //公钥
    EC_POINT *publicKey = NULL;
    //ec_group
    EC_GROUP *ec_group = NULL;
    //ctx
    BN_CTX *ctx = NULL;

    
    //判断输入参数是否为空
    if (inData == NULL || inDataLen == 0 || pubKey == NULL || pubKeyLen == 0 || encryptData == NULL) {
        resultCode = RV_InputErr;
        goto err;
    }
    
    //恢复公钥
    ctx = BN_CTX_new();
    ec_group = EC_GROUP_new_by_curve_name(NID_sm2p256v1);
    publicKey = EC_POINT_new(ec_group);
    int mark = EC_POINT_oct2point(ec_group, publicKey, pubKey, pubKeyLen, ctx);
    if (mark != 1) {
        resultCode = RV_EncErr;
        goto err;
    }
    
    //初始化数据
    ec_key = EC_KEY_new_by_curve_name(NID_sm2p256v1);
    EC_KEY_set_public_key(ec_key, publicKey);
    ec_group = EC_GROUP_new_by_curve_name(NID_sm2p256v1);
    ctx = BN_CTX_new();
    
    //开始加密(使用GMSSL的方法)
    if (!(*encryptData = SM2_do_encrypt(EVP_sm3(), inData, inDataLen, ec_key))) {
        resultCode = RV_EncErr;
        goto err;
    }
    
err:
    if (ec_key != NULL) {
        EC_KEY_free(ec_key);
    }
    if (ec_group != NULL) {
        EC_GROUP_free(ec_group);
    }
    if (ctx != NULL) {
        BN_CTX_free(ctx);
    }
    if (publicKey != NULL) {
        EC_POINT_free(publicKey);
    }
    return resultCode;
}

三、SM2解密算法

1、手动实现

  • 流程


     
    image.png
  • 算法:

1、从密文比特串C=C1||C3||C2中取出C1, 将C1转换成椭圆曲线上的点;

    #define POINT_BIN_LENGTH 65

    unsigned char c1Bin[POINT_BIN_LENGTH];
    unsigned long c1Binlen = POINT_BIN_LENGTH;
    memcpy(c1Bin, encrypt(密文), POINT_BIN_LENGTH);
    EC_POINT  *c1 = EC_POINT_new(ec_group);
    EC_POINT_oct2point(ec_group, c1, c1Bin, c1Binlen, ctx);

2、验证C1, 计算S=[h] C1,如果S是无穷远点,出错退出;

    int resultCode = EC_POINT_is_on_curve(ec_group, c1, ctx);
    if (resultCode) {
        printf("验证C1成功\n");
    }else{
        printf("验证C1失败\n");
    }

3、计算(x2,y2)=[dB] C1

    EC_POINT *dC1 = EC_POINT_new(ec_group);
    EC_POINT_mul(ec_group, dC1, NULL, c1, d, ctx);
    BIGNUM *x2 = BN_new();
    BIGNUM *y2 = BN_new();
    EC_POINT_get_affine_coordinates_GFp(ec_group,
                                        dC1, x2, y2, ctx);

4、计算t=KDF(x2||y2, klen), KDF是密钥派生函数,如果t是全0比特串,出错退出。

    unsigned char x2y2[64] = {0};
    unsigned long x2y2len = 0;
    //x2||y2
    x2y2len += BN_bn2bin(x2, x2y2);
    x2y2len += BN_bn2bin(y2, &x2y2[32]);
    //原文长度klen
    unsigned long klen = encryptLen - (c1Binlen+c3len);
    
    unsigned char t[klen];
    unsigned long tlen = klen;
    sm3_kdf1(EVP_sm3(), x2y2, sizeof(x2y2), t, &tlen);

5、从C=C1||C3||C2中取出C2,计算M’= C2+t。

    unsigned char c2[tlen];
    memcpy(c2, encrypt+c1Binlen+c3len, tlen);
    
    //原文
    unsigned char M[tlen+1];
    unsigned long Mlen = 0;
    for (int i = 0; i < tlen; i ++) {
        M[i] = c2[i] ^ t[i];
        Mlen++;
    }
    M[tlen] = '\0';
    printf("M'-->%s\n",M);

6、计算u=Hash(x2||M’||y2),比较u是否与C3相等,不相等则退出。
7、输出明文M’。

2、使用GMSSL库实现

  • 基于GmSSL 1.2.2 (OpenSSL 1.0.2d)

#define RV_DecErr  0x01000011  //decrypt error

/**
 使用GMSSL解密

 @param d 私钥
 @param encrypt 加密数据
 @param encryptLen 加密数据长度
 @param decryptData 解密数据
 @param decryptDataLen 解密数据长度
 @return 0成功/其它失败
 */
int sm2DecryptByGMSSL(BIGNUM *d,unsigned char *encrypt,unsigned long encryptLen,unsigned char *decryptData,unsigned long *decryptDataLen)
{
    int resultCode = 0;
    
    BN_CTX *ctx = NULL;
    SM2_CIPHERTEXT_VALUE *cv = NULL;
    //C1+C3大小(不包含ciphertext_size,即C2)
    int cvLen = 0;
    SM2_ENC_PARAMS params;
    
    EC_GROUP *ec_group = NULL;
    EC_KEY *ec_key = NULL;
    //bn_prime
    BIGNUM *prime = NULL;
    //c1长度
    int c1Len = 0;
    
    //初始化
    ctx = BN_CTX_new();
    SM2_ENC_PARAMS_init_with_recommended(&params);
    ec_group = EC_GROUP_new_by_curve_name(NID_sm2p256v1);
    ec_key = EC_KEY_new();
    EC_KEY_set_group(ec_key, ec_group);
    EC_KEY_set_private_key(ec_key, d);
    prime = BN_new();
    BN_hex2bn(&prime,_n);
    
    //获取C1(C = C1||C3||C2)-- C为加密数据encryptData
    if (!(cvLen = SM2_CIPHERTEXT_VALUE_size(ec_group, &params, 0))) {
        resultCode = RV_DecErr;
        goto end;
    }
    
    if (!(cv = OPENSSL_malloc(sizeof(SM2_CIPHERTEXT_VALUE)))) {
        resultCode = RV_DecErr;
        goto end;
    }
    
    cv->ephem_point = EC_POINT_new(ec_group);
    cv->ciphertext_size = encryptLen - cvLen;
    cv->ciphertext = OPENSSL_malloc(cv->ciphertext_size);
    if (!cv->ephem_point || !cv->ciphertext) {
        resultCode = RV_DecErr;
        goto end;
    }
    int macTagSize = params.mactag_size<0 ? EVP_MD_size(params.mac_md) : params.mactag_size;
    c1Len = cvLen - macTagSize;
    
    if (!EC_POINT_oct2point(ec_group, cv->ephem_point, encrypt, c1Len, ctx)) {
        resultCode = RV_DecErr;
        goto end;
    }
    
    cv->mactag_size = macTagSize;
    if (cv->mactag_size > 0) {
        memcpy(cv->mactag, encrypt + c1Len, cv->mactag_size);
    }
    
    memcpy(cv->ciphertext, encrypt + c1Len + cv->mactag_size, cv->ciphertext_size);
    
    if (!SM2_do_decrypt(&params, cv, decryptData, decryptDataLen, ec_key))
    {
        resultCode = RV_DecErr;
        goto end;
    }
    *decryptDataLen = cv->ciphertext_size;
   
end:
    if (ctx != NULL) {
        BN_CTX_free(ctx);
    }
    if (cv != NULL) {
        SM2_CIPHERTEXT_VALUE_free(cv);
    }
    if (ec_group != NULL) {
        EC_GROUP_free(ec_group);
    }
    if (ec_key != NULL) {
        EC_KEY_free(ec_key);
    }
    if (prime != NULL) {
        BN_free(prime);
    }
    return resultCode;
}
  • 基于GmSSL 2.5.4 - OpenSSL 1.1.0d 3 Sep 2019
/**
 使用GMSSL解密
 
 @param cv 加密数据
 @param d 私钥
 @param decryptData 解密数据
 @param decryptDataLen 解密数据长度
 @return 0成功/其它失败
 */
  int sm2DecryptByGMSSL(SM2CiphertextValue *cv,BIGNUM *d,unsigned char *decryptData,unsigned long *decryptDataLen)
{
    int resultCode = 0;
    BN_CTX *ctx = NULL;
    
    EC_GROUP *ec_group = NULL;
    EC_KEY *ec_key = NULL;
    //bn_prime
    BIGNUM *prime = NULL;
    
    //判断输入参数是否为空
    if (cv == NULL || d == NULL || decryptData == NULL) {
        resultCode = RV_InputErr;
        goto end;
    }

    
    //初始化
    ctx = BN_CTX_new();
    ec_group = EC_GROUP_new_by_curve_name(NID_sm2p256v1);
    //设置私钥
    ec_key = EC_KEY_new();
    EC_KEY_set_group(ec_key, ec_group);
    EC_KEY_set_private_key(ec_key, d);
    //prime
    prime = BN_new();
    BN_hex2bn(&prime,SM2_n);
    
    //C = C1||C3||C2 -- C为加密数据encryptData
    if (!SM2_do_decrypt(EVP_sm3(), cv, decryptData, decryptDataLen, ec_key))
    {
        resultCode = RV_DecErr;
        goto end;
    }
    printf("\n Decrypt Data-->%s\n",decryptData);
end:
    if (ctx != NULL) {
        BN_CTX_free(ctx);
    }
    if (ec_group != NULL) {
        EC_GROUP_free(ec_group);
    }
    if (ec_key != NULL) {
        EC_KEY_free(ec_key);
    }
    if (prime != NULL) {
        BN_free(prime);
    }
    if (d != NULL) {
        BN_free(d);
    }
    return resultCode;
}

四、结论

  • 想要成功解密出原文,必须是公钥PB和私钥dB是匹配的,即满足PB=[dB]G,原文经过两次与同一比特串的异或计算,结果还是原文。
posted @ 2020-05-08 19:06  Bigben  阅读(2749)  评论(0编辑  收藏  举报