ios - iOS 10 之前带有 OAEP 填充 sha256 的 objective-c RSA

Question

我正在用RSA加密方法在iPhone上研究一种加密方法，目前我可以用这种方法获得加密字符串，该字符串被服务器成功解密。

SecKeyRef keyRef = [self addPublicKey:pubKey];

SecKeyAlgorithm algorithm = kSecKeyAlgorithmRSAEncryptionOAEPSHA256;

if (!keyRef) {
    return nil;
}

BOOL canEncrypt =  SecKeyIsAlgorithmSupported(keyRef, kSecKeyOperationTypeEncrypt, algorithm);

if (canEncrypt) {
    CFErrorRef error = NULL;
    NSData *encryptedData = (NSData *)CFBridgingRelease(
                                                        SecKeyCreateEncryptedData(keyRef, algorithm, (__bridge CFDataRef) content, &error)
    );

    if (encryptedData) {
        return encryptedData;
    }else{
        NSError *err = CFBridgingRelease(error);
        NSLog(@"Ocurrió un error %@", err.localizedDescription);
        return nil;
    }
}

此方法适用于 ios 10 及更新版本，我需要知道如何在以前的 ios 版本中设置算法，我的代码如下

SecKeyRef keyRef = [self addPublicKey:pubKey];
if (!keyRef) {
    return nil;
}

size_t cipherBufferSize = SecKeyGetBlockSize(keyRef);
uint8_t *cipherBuffer = malloc(cipherBufferSize * sizeof(uint8_t));
memset((void *)cipherBuffer, 0*0, cipherBufferSize);

NSData *plainTextBytes = content;
size_t blockSize = cipherBufferSize - 11;
size_t blockCount = (size_t)ceil([plainTextBytes length] / (double)blockSize);

NSMutableData *encryptedData = [NSMutableData dataWithCapacity:0];

for (int i=0; i<blockCount; i++) {

    int bufferSize = (int)MIN(blockSize,[plainTextBytes length] - i * blockSize);
    NSData *buffer = [plainTextBytes subdataWithRange:NSMakeRange(i * blockSize, bufferSize)];
    OSStatus status = SecKeyEncrypt(keyRef,
                                    kSecPaddingOAEP,
                                    (const uint8_t *)[buffer bytes],
                                    [buffer length],
                                    cipherBuffer,
                                    &cipherBufferSize);

    if (status == noErr){
        NSData *encryptedBytes = [NSData dataWithBytes:(const void *)cipherBuffer length:cipherBufferSize];
        [encryptedData appendData:encryptedBytes];

    }else{

        if (cipherBuffer) {
            free(cipherBuffer);
        }
        return nil;
    }
}
if (cipherBuffer) free(cipherBuffer);

到目前为止我可以看到在 ios 10 版本中你可以用这一行设置算法

SecKeyAlgorithm algorithm = kSecKeyAlgorithmRSAEncryptionOAEPSHA256;

我的问题是，我如何在ios的早期版本中获得该算法，我发布的第二个代码无法解密。

谢谢你的帮助

Answer 1

如果您使用带有 SecKeyEncrypt 的 OAEP 填充，您只能使用 kSecPaddingOAEP，它是 SHA1。遗憾的是，您不能将 OAEP SHA256 与 SecKeyEncrypt 一起使用。