NSString的AES加密？

Question

我正在为iOS实现一些解密代码,用于源自我无法控制的服务器上的消息.所以解密要求是:

Cipher Method : AES256
Cipher Mode: ECB
Padding: PKCS5Padding

由于我最初的试验未能解密.所以我玩了一些测试向量,看看我使用的代码是对的,

这是加密数据的代码:

NSString+AESCrypt.h
-------------------
#import <Foundation/Foundation.h>
#import "NSData+AESCrypt.h"

@interface NSString (AESCrypt)

- (NSString *)AES256EncryptWithKey:(NSString *)key;
- (NSString *)AES256DecryptWithKey:(NSString *)key;

@end


NSString+AESCrypt.m
-------------------
#import "NSString+AESCrypt.h"

@implementation NSString (AESCrypt)

- (NSString *)AES256EncryptWithKey:(NSString *)key
{
   NSData *plainData = [self dataUsingEncoding:NSUTF8StringEncoding];
   NSData *encryptedData = [plainData AES256EncryptWithKey:key];

   NSString *encryptedString = [encryptedData base64Encoding];

   return encryptedString;
}

- (NSString *)AES256DecryptWithKey:(NSString *)key
{
   NSData *encryptedData = [NSData dataWithBase64EncodedString:self];
   NSData *plainData = [encryptedData AES256DecryptWithKey:key];

   NSString *plainString = [[NSString alloc] initWithData:plainData encoding:NSUTF8StringEncoding];

   return [plainString autorelease];
}

@end


NSData+AESCrypt.h
-------------------
#import <Foundation/Foundation.h>

@interface NSData (AESCrypt)

- (NSData *)AES256EncryptWithKey:(NSString *)key;
- (NSData *)AES256DecryptWithKey:(NSString *)key;

+ (NSData *)dataWithBase64EncodedString:(NSString *)string;
- (id)initWithBase64EncodedString:(NSString *)string;

- (NSString *)base64Encoding;
- (NSString *)base64EncodingWithLineLength:(NSUInteger)lineLength;

- (BOOL)hasPrefixBytes:(const void *)prefix length:(NSUInteger)length;
- (BOOL)hasSuffixBytes:(const void *)suffix length:(NSUInteger)length;

@end

NSData+AESCrypt.m
-------------------
#import "NSData+AESCrypt.h"
#import <CommonCrypto/CommonCryptor.h>

static char encodingTable[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 NSData (AESCrypt)

- (NSData *)AES256EncryptWithKey:(NSString *)key
{
   // 'key' should be 32 bytes for AES256, will be null-padded otherwise
   char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused)
   bzero( keyPtr, sizeof( keyPtr ) ); // fill with zeroes (for padding)

   // fetch key data
   [key getCString:keyPtr maxLength:sizeof( keyPtr ) encoding:NSUTF8StringEncoding];

   NSUInteger dataLength = [self length];

   //See the doc: For block ciphers, the output size will always be less than or 
   //equal to the input size plus the size of one block.
   //That's why we need to add the size of one block here
   size_t bufferSize = dataLength + kCCBlockSizeAES128;
   void *buffer = malloc( bufferSize );

   size_t numBytesEncrypted = 0;
   CCCryptorStatus cryptStatus = CCCrypt( kCCEncrypt, kCCAlgorithmAES128, kCCOptionECBMode + kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesEncrypted );
   if( cryptStatus == kCCSuccess )
   {
      //the returned NSData takes ownership of the buffer and will free it on deallocation
      return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
   }

   free( buffer ); //free the buffer
   return nil;
}

- (NSData *)AES256DecryptWithKey:(NSString *)key
{
   // 'key' should be 32 bytes for AES256, will be null-padded otherwise
   char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
   bzero( keyPtr, sizeof( keyPtr ) ); // fill with zeroes (for padding)

   // fetch key data
   [key getCString:keyPtr maxLength:sizeof( keyPtr ) encoding:NSUTF8StringEncoding];

   NSUInteger dataLength = [self length];

   //See the doc: For block ciphers, the output size will always be less than or 
   //equal to the input size plus the size of one block.
   //That's why we need to add the size of one block here
   size_t bufferSize = dataLength + kCCBlockSizeAES128;
   void *buffer = malloc( bufferSize );

   size_t numBytesDecrypted = 0;
   CCCryptorStatus cryptStatus = CCCrypt( kCCDecrypt, kCCAlgorithmAES128, kCCOptionECBMode + kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesDecrypted );

   if( cryptStatus == kCCSuccess )
   {
      //the returned NSData takes ownership of the buffer and will free it on deallocation
      return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
   }

   free( buffer ); //free the buffer
   return nil;
}

#pragma mark -

+ (NSData *)dataWithBase64EncodedString:(NSString *)string
{
   return [[[NSData allocWithZone:nil] initWithBase64EncodedString:string] autorelease];
}

- (id)initWithBase64EncodedString:(NSString *)string
{
   NSMutableData *mutableData = nil;

   if( string )
   {
      unsigned long ixtext = 0;
      unsigned long lentext = 0;
      unsigned char ch = 0;
      unsigned char inbuf[4], outbuf[3];
      short i = 0, ixinbuf = 0;
      BOOL flignore = NO;
      BOOL flendtext = NO;
      NSData *base64Data = nil;
      const unsigned char *base64Bytes = nil;

      // Convert the string to ASCII data.
      base64Data = [string dataUsingEncoding:NSASCIIStringEncoding];
      base64Bytes = [base64Data bytes];
      mutableData = [NSMutableData dataWithCapacity:base64Data.length];
      lentext = base64Data.length;

      while( YES )
      {
         if( ixtext >= lentext ) break;
         ch = base64Bytes[ixtext++];
         flignore = NO;

         if( ( ch >= 'A' ) && ( ch <= 'Z' ) ) ch = ch - 'A';
         else if( ( ch >= 'a' ) && ( ch <= 'z' ) ) ch = ch - 'a' + 26;
         else if( ( ch >= '0' ) && ( ch <= '9' ) ) ch = ch - '0' + 52;
         else if( ch == '+' ) ch = 62;
         else if( ch == '=' ) flendtext = YES;
         else if( ch == '/' ) ch = 63;
         else flignore = YES;

         if( ! flignore )
         {
            short ctcharsinbuf = 3;
            BOOL flbreak = NO;

            if( flendtext ) 
            {
               if( ! ixinbuf ) break;
               if( ( ixinbuf == 1 ) || ( ixinbuf == 2 ) ) ctcharsinbuf = 1;
               else ctcharsinbuf = 2;
               ixinbuf = 3;
               flbreak = YES;
            }

            inbuf [ixinbuf++] = ch;

            if( ixinbuf == 4 ) 
            {
               ixinbuf = 0;
               outbuf [0] = ( inbuf[0] << 2 ) | ( ( inbuf[1] & 0x30) >> 4 );
               outbuf [1] = ( ( inbuf[1] & 0x0F ) << 4 ) | ( ( inbuf[2] & 0x3C ) >> 2 );
               outbuf [2] = ( ( inbuf[2] & 0x03 ) << 6 ) | ( inbuf[3] & 0x3F );

               for( i = 0; i < ctcharsinbuf; i++ )
                  [mutableData appendBytes:&outbuf[i] length:1];
            }

            if( flbreak )  break;
         }
      }
   }

   self = [self initWithData:mutableData];
   return self;
}

#pragma mark -

- (NSString *)base64Encoding
{
   return [self base64EncodingWithLineLength:0];
}

- (NSString *)base64EncodingWithLineLength:(NSUInteger)lineLength
{
   const unsigned char   *bytes = [self bytes];
   NSMutableString *result = [NSMutableString stringWithCapacity:self.length];
   unsigned long ixtext = 0;
   unsigned long lentext = self.length;
   long ctremaining = 0;
   unsigned char inbuf[3], outbuf[4];
   unsigned short i = 0;
   unsigned short charsonline = 0, ctcopy = 0;
   unsigned long ix = 0;

   while( YES )
   {
      ctremaining = lentext - ixtext;
      if( ctremaining <= 0 ) break;

      for( i = 0; i < 3; i++ )
      {
         ix = ixtext + i;
         if( ix < lentext ) inbuf[i] = bytes[ix];
         else inbuf [i] = 0;
      }

      outbuf [0] = (inbuf [0] & 0xFC) >> 2;
      outbuf [1] = ((inbuf [0] & 0x03) << 4) | ((inbuf [1] & 0xF0) >> 4);
      outbuf [2] = ((inbuf [1] & 0x0F) << 2) | ((inbuf [2] & 0xC0) >> 6);
      outbuf [3] = inbuf [2] & 0x3F;
      ctcopy = 4;

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

      for( i = 0; i < ctcopy; i++ )
         [result appendFormat:@"%c", encodingTable[outbuf[i]]];

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

      ixtext += 3;
      charsonline += 4;

      if( lineLength > 0 )
      {
         if( charsonline >= lineLength )
         {
            charsonline = 0;
            [result appendString:@"\n"];
         }
      }
   }

   return [NSString stringWithString:result];
}

#pragma mark -

- (BOOL)hasPrefixBytes:(const void *)prefix length:(NSUInteger)length
{
   if( ! prefix || ! length || self.length < length ) return NO;
   return ( memcmp( [self bytes], prefix, length ) == 0 );
}

- (BOOL)hasSuffixBytes:(const void *)suffix length:(NSUInteger)length
{
   if( ! suffix || ! length || self.length < length ) return NO;
   return ( memcmp( ((const char *)[self bytes] + (self.length - length)), suffix, length ) == 0 );
}

@end

我执行上面的函数并使用以下代码将结果数据写入日志:

NSString * _secret = @"6bc1bee22e409f96e93d7e117393172a";
NSString * _key = @"603deb1015ca71be2b73aef0857d77811f352c073b6108d72d9810a30914dff4";

NSString *encryptedString = [_secret AES256EncryptWithKey:_key];
NSLog(@"Encrypted ID : %@", encryptedString);

NSString *decryptedString = [encryptedString AES256DecryptWithKey:_key];
NSLog(@"Decrypted ID : %@", decryptedString);

从测试向量开始,加密密码应为:

f3eed1bdb5d2a03c064b5a7e3db181f8

结果日志:

2011-10-19 13:32:41.640 Ticket[2215:707] Encrypted ID : XWLsnTQvocXNkAqVisEgWTCPdYR6KPoIojezjN3fn/wuytQkpUZnNbzUoT4peeTK
2011-10-19 13:32:41.641 Ticket[2215:707] Decrypted ID : 6bc1bee22e409f96e93d7e117393172a

我知道这个加密ID在Base64中,但即使我将其转换为HEX,实际输出也会因结果而异.

我忘了什么选择？NSData的编码是否返回了其他内容......？

因此,如果有人能指引我走上正确的道路,干杯.

Answer 1

我认为问题在于测试向量页面假设这些打印的十六进制值是二进制文件而不是文本：字符串“6b”看起来确实是这样编码的：0x3662。

\n\n

为了获得正确的测试字符串，您必须首先对其进行编码。您的字符串应以此开头：@“k \ xc3 \ x81 \ xc2 \ xbe \ xc3 \ xa2 ....”。如果使用 utf-8 进行编码，该字符串将产生正确的十六进制表示形式。

\n\n

NSData 您应该使用十六进制字符串初始化 来测试您的 aes 加密
，或者必须首先解码 utf-8 以将所有内容打包到字符串中。但要小心：经常有一些符号无法表示/打印，甚至更糟糕：如果您的 tesdata 或密码包含零字节，那么这将导致一些问题，因为它经常用作字符串中的终止符号，而字符串通常包含仅可读字符。（不知道这如何与 交互NSString）
\也不使用第一个变体创建NSData十六进制字符串，然后将该数据转换为NSString

\n