使用RSA在iOS上签名和验证

Question

如何使用RSA密钥在iOS上签名和验证某些数据(最好使用系统自己的libcommonCrypto)？

Answer 1

由于几乎没有关于在StackOverflow和Apple文档上找到的签名和验证的任何知识,我不得不手动浏览iOS头文件并找到SecKeyRawSign和SecKeyRawVerify.以下代码行似乎有效.

签署NSData(使用带有RSA的SHA256):

NSData* PKCSSignBytesSHA256withRSA(NSData* plainData, SecKeyRef privateKey)
{
    size_t signedHashBytesSize = SecKeyGetBlockSize(privateKey);
    uint8_t* signedHashBytes = malloc(signedHashBytesSize);
    memset(signedHashBytes, 0x0, signedHashBytesSize);

    size_t hashBytesSize = CC_SHA256_DIGEST_LENGTH;
    uint8_t* hashBytes = malloc(hashBytesSize);
    if (!CC_SHA256([plainData bytes], (CC_LONG)[plainData length], hashBytes)) {
        return nil;
    }

    SecKeyRawSign(privateKey,
                  kSecPaddingPKCS1SHA256,
                  hashBytes,
                  hashBytesSize,
                  signedHashBytes,
                  &signedHashBytesSize);

    NSData* signedHash = [NSData dataWithBytes:signedHashBytes
                                        length:(NSUInteger)signedHashBytesSize];

    if (hashBytes)
        free(hashBytes);
    if (signedHashBytes)
        free(signedHashBytes);

    return signedHash;
}

验证(使用带RSA的SHA256):

BOOL PKCSVerifyBytesSHA256withRSA(NSData* plainData, NSData* signature, SecKeyRef publicKey)
{
    size_t signedHashBytesSize = SecKeyGetBlockSize(publicKey);
    const void* signedHashBytes = [signature bytes];

    size_t hashBytesSize = CC_SHA256_DIGEST_LENGTH;
    uint8_t* hashBytes = malloc(hashBytesSize);
    if (!CC_SHA256([plainData bytes], (CC_LONG)[plainData length], hashBytes)) {
        return nil;
    }

    OSStatus status = SecKeyRawVerify(publicKey,
                                      kSecPaddingPKCS1SHA256,
                                      hashBytes,
                                      hashBytesSize,
                                      signedHashBytes,
                                      signedHashBytesSize);

    return status == errSecSuccess;
}

替代方案(OpenSSL):

有一个非常好的替代品可以直接使用OpenSSL而不是libCommonCrypto.MIHCrypto是一个精心设计的OpenSSL Objective-C包装器库,它使得加密技术变得非常容易.请参阅下面的示例.

生成密钥很简单:

MIHAESKeyFactory *factory = [[MIHAESKeyFactory alloc] init];
id<MIHSymmetricKey> aesKey = [factory generateKey];

或者从文件加载密钥:

NSData *privateKeyData = [[NSFileManager defaultManager] contentsAtPath:"mykey.pem"];
MIHRSAPrivateKey *privateKey = [[MIHRSAPrivateKey alloc] initWithData:privateKeyData];

现在签名:

NSError *signingError = nil;
NSData *message = // load something to sign from somewhere
NSData *signature = [privateKey signWithSHA256:message error:&signingError]

有关更多示例,请浏览MIHCrypto页面.