将uint8_t转换为RSA解密中的NSString

Question

我试图实现RSA算法，并且我跟着苹果reference。 但我遇到问题将uint8_t转换为NSData到NSString。

我已经做了在reference

-(void)test{ 
    [self generateKeyPairPlease]; 
    NSData *data = [self encryptWithPublicKey]; //All goes well until here 
    [self decryptWithPrivateKey:data]; 

} 

定义加密我这样做使far..These功能..

- (NSData *)encryptWithPublicKey 
{ 
    OSStatus status = noErr; 

    size_t cipherBufferSize; 
    uint8_t *cipherBuffer;      // 1 

// [cipherBufferSize] 
    const uint8_t dataToEncrypt[] = "the quick brown fox jumps " 
          "over the lazy dog\0"; // 2 
    size_t dataLength = sizeof(dataToEncrypt)/sizeof(dataToEncrypt[0]); 

    SecKeyRef publicKey = NULL;         // 3 

    NSData * publicTag = [NSData dataWithBytes:publicKeyIdentifier 
      length:strlen((const char *)publicKeyIdentifier)]; // 4 

    NSMutableDictionary *queryPublicKey = 
          [[NSMutableDictionary alloc] init]; // 5 

    [queryPublicKey setObject:(__bridge id)kSecClassKey forKey:(__bridge id)kSecClass]; 
    [queryPublicKey setObject:publicTag forKey:(__bridge id)kSecAttrApplicationTag]; 
    [queryPublicKey setObject:(__bridge id)kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType]; 
    [queryPublicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef]; 
                   // 6 

    status = SecItemCopyMatching 
    ((__bridge CFDictionaryRef)queryPublicKey, (CFTypeRef *)&publicKey); // 7 

// Allocate a buffer 

    cipherBufferSize = SecKeyGetBlockSize(publicKey); 
    cipherBuffer = malloc(cipherBufferSize); 

// Error handling 

    if (cipherBufferSize < sizeof(dataToEncrypt)) { 
     // Ordinarily, you would split the data up into blocks 
     // equal to cipherBufferSize, with the last block being 
     // shorter. For simplicity, this example assumes that 
     // the data is short enough to fit. 
     printf("Could not decrypt. Packet too large.\n"); 
     return NULL; 
    } 

    // Encrypt using the public. 
    status = SecKeyEncrypt( publicKey, 
           kSecPaddingPKCS1, 
           dataToEncrypt, 
           (size_t) dataLength, 
           cipherBuffer, 
           &cipherBufferSize 
           );        // 8 

// Error handling 
// Store or transmit the encrypted text 

    if (publicKey) CFRelease(publicKey); 

    NSData *encryptedData = [NSData dataWithBytes:cipherBuffer length:dataLength]; 

    free(cipherBuffer); 

    return encryptedData; 
} 

但decryptWithPrivateKey我能不能转换uint8_t *plainBuffer（解密结果）到NSString。首先我试图把它转换成NSData打印时用NSLog它正确显示字节，但是NSData没有转换成字符串。

- (void)decryptWithPrivateKey: (NSData *)dataToDecrypt 
{ 
    OSStatus status = noErr; 

    size_t cipherBufferSize = [dataToDecrypt length]; 
    uint8_t *cipherBuffer = (uint8_t *)[dataToDecrypt bytes]; 

    size_t plainBufferSize; 
    uint8_t *plainBuffer; 

    SecKeyRef privateKey = NULL; 

    NSData * privateTag = [NSData dataWithBytes:privateKeyIdentifier 
             length:strlen((const char *)privateKeyIdentifier)]; 

    NSMutableDictionary *queryPrivateKey = [[NSMutableDictionary alloc] init]; 

    // Set the private key query dictionary. 
    [queryPrivateKey setObject:(__bridge id)kSecClassKey forKey:(__bridge id)kSecClass]; 
    [queryPrivateKey setObject:privateTag forKey:(__bridge id)kSecAttrApplicationTag]; 
    [queryPrivateKey setObject:(__bridge id)kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType]; 
    [queryPrivateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef]; 
    // 1 

    status = SecItemCopyMatching 
    ((__bridge CFDictionaryRef)queryPrivateKey, (CFTypeRef *)&privateKey); // 2 

    // Allocate the buffer 
    plainBufferSize = SecKeyGetBlockSize(privateKey); 
    plainBuffer = malloc(plainBufferSize); 

    if (plainBufferSize < cipherBufferSize) { 
     // Ordinarily, you would split the data up into blocks 
     // equal to plainBufferSize, with the last block being 
     // shorter. For simplicity, this example assumes that 
     // the data is short enough to fit. 
     printf("Could not decrypt. Packet too large.\n"); 
     return; 
    } 

    // Error handling 

    status = SecKeyDecrypt( privateKey, 
          kSecPaddingPKCS1, 
          cipherBuffer, 
          cipherBufferSize, 
          plainBuffer, 
          &plainBufferSize 
          );        // 3 

    //******************************************************************************* 
    // Not able to convert uint8_t *plainBuffer to string 
    // I also tried to convert it into NSData and then try to convert it into NSString but can't 
    //What Should i do here to get string back 


    if(privateKey) CFRelease(privateKey); 
} 
@end 

我想知道如何解密结果uint8_t plainBuffer转换为NSData到NSString或者干脆NSString，使我得到我的字符串back.For我的加密和密钥生成代码，请参阅本reference。

在此先感谢..

Answer 1

我管理由以下这code。它的相同的代码来解决我的问题，但串的编码different.In encryptWithPublicKey功能我已经使用

uint8_t *dataToEncrypt= (uint8_t *)[@"the quick brown fox jumps over the lazy dog" UTF8String];

代替

const uint8_t dataToEncrypt[] = "the quick brown fox jumps " "over the lazy dog\0";

和decryptWithPrivateKey我已经使用这个解码

NSData *decryptedData = [NSData dataWithBytes:plainBuffer length:plainBufferSize]; 
NSString *decryptedString = [[[NSString alloc] initWithData:decryptedData encoding:NSUTF8StringEncoding] autorelease]; 

Answer 2

最有可能的问题是，你打电话+[stringWithCharacters:length:]，其预计Unicode字符（更准确地说，UTF-16代码点），但你可能有UTF-8或其他8位编码。

您必须知道您的编码，因此您可以拨打+[stringWithCString:encoding:]（或者，如果是UTF-8，则为+[stringWithUTF8String:]）。

请注意，与stringWithCharacters不同，这些方法不占用长度，并且期望您的数据以空值终止。因此，除非您确定数据总是有终止符，否则您应该明确检查它，或者分配字符串，然后调用-[initWithBytes:length:encoding:]。

如果您不知道在加密之前明文处于什么字符集，您需要了解。作为一个人，你通常可以通过查看它，特别是如果它主要是ASCII。用缓冲区创建一个NSData并记录下来并查看十六进制数。如果是UTF-16，则ASCII字符将与空值交替，因此'Hello'将为48 00 65 00 6C 00 6C 00 6F 00。但是电脑不会做出很好的猜测。 （原因+[stringWithContentsOfFile:usedEncoding:error:]通常会得到它的权利是，它看起来在扩展属性com.apple.TextEncoding，当他们保存一个文件，其中最Cocoa程序写。）

Answer 3

我知道这个问题是旧的，标记为解决，但我有一个类似的问题来到这里。 我发现了什么是有似乎是在加密方法的错误在该行

NSData *encryptedData = [NSData dataWithBytes:cipherBuffer length:dataLength]; 

数据长度是错误的变量这里的苹果文档。我用cipherbuffersize替换它为

NSData *encryptedData = [NSData dataWithBytes:cipherBuffer length:cipherBufferSize]; 

和所有东西现在对我来说很好。我希望它对于别人比我有用。