RSA加密解密在iphone [英] RSA Encryption-Decryption in iphone

问题描述

我正在开发Iphone应用程序。我使用Security / Security.h框架的SecKeyGeneratePair方法。我得到公共&私钥作为SecKeyRef对象。我可以访问该键或将其值打印到控制台吗？我可以从它获得NSString或NSData对象吗？当我使用NSLog打印密钥到控制台我得到。我们可以通过网络传递这些关键对象到其他应用程序可能在java？我们可以在iphone应用程序中加密一些文本，发送到服务器，使用密钥发送解密服务器端的文本？

I am developing Iphone application. I have used SecKeyGeneratePair method of Security/Security.h framework. I am getting public & private keys as SecKeyRef objects. Can I access the key or print its value to console? Can I get NSString or NSData object from it ? When i print the key to console using NSLog I am getting . Can we pass these key objects over network to other application which might be in java? Can we encrypt some text in iphone application, send it to server, using the key sent decrypt the text on server side ?

编辑添加
感谢Alex Reynolds的快速回复。在RSA加密的情况下，我必须首先生成一个以SecKeyRef对象形式的密钥对。然后我们将该参考传递给SecKeyEncrypt& SecKeyDecrypt方法。当我加密和在本地解密它工作完美，但如果我尝试发送密钥&加密数据到服务器&解密在服务器（java实现）端，我不能将SecKeyRef对象作为键值传递给服务器。在java中，我们必须获取string或byte数组格式的字符串传递给加密方法。我们可以获得对存储在对象SecKeyRef（这是NSCFType对象）中的数据的访问吗？这是一个结构__SecKey。

Edited to add Thanks Alex Reynolds for your quick response. In case of RSA Encryption first I have to generate a key pair which is in the form of SecKeyRef objects. Then we will pass that reference to SecKeyEncrypt & SecKeyDecrypt methods. when i encrypt & decrypt locally it is working perfect but if i try to send the key & encrypted data to server & decrypt at server(java implementation) side, I am not able to pass the SecKeyRef object to server as a key value. In java we have to get the string in string or byte array format to pass to the encryption method. Can we get the access to the data stored in object SecKeyRef (which is NSCFType object)? which is a struct __SecKey.

推荐答案

考虑使用NSData获取字符串值，也许使用Base64或其他形式的编码当通过网络（然后解码从Base64到任何在Java）。

Consider using NSData to get the string value, and perhaps use Base64 or some other form of encoding when passing over the network (and then decoding from Base64 to whatever in Java).

以下是一些可能有助于您开始使用的代码示例。我在这里做一个HMAC-SHA1签名（'digest'），但是你的RSA案件的一般想法是一样的：

Here's an example of some code that might help you get started. I'm doing a HMAC-SHA1 signature ('digest') here, but the general idea is the same for your RSA case:

#import <Foundation/NSString.h>
#import <CommonCrypto/CommonHMAC.h>
#import <CommonCrypto/CommonDigest.h>

@interface NSString (NSStringAdditions)

+ (NSString *) base64StringFromData:(NSData *)data length:(int)length;
- (NSString *) base64StringWithHMACSHA1Digest:(NSString *)secretKey;

@end

-------------------------------------------

#import "NSStringAdditions.h"

static char base64EncodingTable[64] = {
  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
  'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
  'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
  'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
};

@implementation NSString (NSStringAdditions)

- (NSString *) base64StringWithHMACSHA1Digest:(NSString *)secretKey {
  unsigned char digest[CC_SHA1_DIGEST_LENGTH];
  char *keyCharPtr = strdup([secretKey UTF8String]);
  char *dataCharPtr = strdup([self UTF8String]);

  CCHmacContext hctx;
  CCHmacInit(&hctx, kCCHmacAlgSHA1, keyCharPtr, strlen(keyCharPtr));
  CCHmacUpdate(&hctx, dataCharPtr, strlen(dataCharPtr));
  CCHmacFinal(&hctx, digest);
  NSData *encryptedStringData = [NSData dataWithBytes:digest length:CC_SHA1_DIGEST_LENGTH];

  free(keyCharPtr);
  free(dataCharPtr);

  return [NSString base64StringFromData:encryptedStringData length:[encryptedStringData length]];
}

+ (NSString *) base64StringFromData: (NSData *)data length: (int)length {
  unsigned long ixtext, lentext;
  long ctremaining;
  unsigned char input[3], output[4];
  short i, charsonline = 0, ctcopy;
  const unsigned char *raw;
  NSMutableString *result;

  lentext = [data length]; 
  if (lentext < 1)
    return @"";
  result = [NSMutableString stringWithCapacity: lentext];
  raw = [data bytes];
  ixtext = 0; 

  while (true) {
    ctremaining = lentext - ixtext;
    if (ctremaining <= 0) 
       break;        
    for (i = 0; i < 3; i++) { 
       unsigned long ix = ixtext + i;
       if (ix < lentext)
          input[i] = raw[ix];
       else
          input[i] = 0;
    }
    output[0] = (input[0] & 0xFC) >> 2;
    output[1] = ((input[0] & 0x03) << 4) | ((input[1] & 0xF0) >> 4);
    output[2] = ((input[1] & 0x0F) << 2) | ((input[2] & 0xC0) >> 6);
    output[3] = input[2] & 0x3F;
    ctcopy = 4;

    switch (ctremaining) {
      case 1: 
         ctcopy = 2; 
         break;
      case 2: 
         ctcopy = 3; 
         break;
    }

    for (i = 0; i < ctcopy; i++)
       [result appendString: [NSString stringWithFormat: @"%c", base64EncodingTable[output[i]]]];

    for (i = ctcopy; i < 4; i++)
       [result appendString: @"="];

    ixtext += 3;
    charsonline += 4;

    if ((length > 0) && (charsonline >= length))
      charsonline = 0;

    return result;
 }

 @end

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