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我正在實施iOS的一些解密代碼，用於源自我無法控制的服務器上的消息。所以解密要求是：對NSString的AES加密？
Cipher Method : AES256
Cipher Mode: ECB
Padding: PKCS5Padding
由於我最初的試驗未能解密。所以我打得四處some test vectors看到我使用是正確的代碼，
這是對數據加密的代碼：
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
我執行上述功能和產生的數據寫入日誌本代碼：
NSString * _secret = @"6bc1bee22e409f96e93d7e117393172a";
NSString * _key = @"603deb1015ca71be2b73aef0857d77811f352c073b6108d72d9810a30914dff4";
NSString *encryptedString = [_secret AES256EncryptWithKey:_key];
NSLog(@"Encrypted ID : %@", encryptedString);
NSString *decryptedString = [encryptedString AES256DecryptWithKey:_key];
NSLog(@"Decrypted ID : %@", decryptedString);
如從測試向量，加密的密碼應該是這樣的：
個f3eed1bdb5d2a03c064b5a7e3db181f8
結果日誌：
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
我知道這個加密ID是Base64編碼，但仍即使我將其轉換爲十六進制，實際輸出的結果而變化。
我忘了什麼選項？ NSData的編碼是否返回了其他內容...？
所以，如果有人能指引我走上正確的道路，那就太好了，乾杯。
歡迎SO;祝賀你的第一個問題，寫得很清楚，寫得很好。 – Cyrille