本文转载至 http://blog.csdn.net/zaitianaoxiang/article/details/6650478
- 原文链接 : http://www.yifeiyang.net/iphone-development-techniques-of-data-papers-2-iphone-encryption-program/
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iPhone开发技巧之数据篇（2）—iPhone程序中的加密处理
CCCrypt
在Objective-C语言中，加密时常用到CCCrypt(3cc)Mac OS X Manual Page。下面的代码使用 CCCrypt() ，给 NSData 类增加了AES256EncryptWithKey, AES256DecryptWithKey 方法.
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#import <CommonCrypto/CommonCryptor.h> @implementation NSData (Additions) @class NSString; - (NSData *)AES256EncryptWithKey:(NSString *)key { char keyPtr[kCCKeySizeAES256+1]; bzero(keyPtr, sizeof(keyPtr)); [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [self length]; size_t bufferSize = dataLength + kCCBlockSizeAES128; void *buffer = malloc(bufferSize); size_t numBytesEncrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode, keyPtr, kCCBlockSizeAES128, NULL, [self bytes], dataLength, buffer, bufferSize, &numBytesEncrypted); if (cryptStatus == kCCSuccess) { return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted]; } free(buffer); return nil; } - (NSData *)AES256DecryptWithKey:(NSString *)key { char keyPtr[kCCKeySizeAES256+1]; bzero(keyPtr, sizeof(keyPtr)); [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [self length]; size_t bufferSize = dataLength + kCCBlockSizeAES128; void *buffer = malloc(bufferSize); size_t numBytesDecrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode, keyPtr, kCCBlockSizeAES128, NULL, [self bytes], dataLength, buffer, bufferSize, &numBytesDecrypted); if (cryptStatus == kCCSuccess) { return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted]; } free(buffer); return nil; } @end使用的时候就像使用NSData一样。
base64encoding
有的时候需要向服务器上传递base64加密的数据，这个时候我们就可以像下面，给 NSData类追加newStringInBase64FromData 方法。
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- (NSString *)newStringInBase64FromData { NSMutableString *dest = [[NSMutableString alloc] initWithString:@""]; unsigned char * working = (unsigned char *)[self bytes]; int srcLen = [self length]; for (int i=0; i<srcLen; i += 3) { for (int nib=0; nib<4; nib++) { int byt = (nib == 0)?0:nib-1; int ix = (nib+1)*2; if (i+byt >= srcLen) break; unsigned char curr = ((working[i+byt] << (8-ix)) & 0x3F); if (i+nib < srcLen) curr |= ((working[i+nib] >> ix) & 0x3F); [dest appendFormat:@"%c", base64[curr]]; } } return dest; }同样，使用的时候就像使用NSData一样。
最终的代码如下所示 ：
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// // NSDataAdditions.h // // Copyright 2010 __MyCompanyName__. All rights reserved. // #import <Foundation/Foundation.h> @class NSString; @interface NSData (Additions) - (NSData *)AES256EncryptWithKey:(NSString *)key; - (NSData *)AES256DecryptWithKey:(NSString *)key; - (NSString *)newStringInBase64FromData; @end // ----------------------------------------------------------------------------------- // // NSDataAdditions.m // // Copyright 2010 __MyCompanyName__. All rights reserved. // #import "NSDataAdditions.h" #import <CommonCrypto/CommonCryptor.h> static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; @implementation NSData (Additions) @class NSString; - (NSData *)AES256EncryptWithKey:(NSString *)key { char keyPtr[kCCKeySizeAES256+1]; bzero(keyPtr, sizeof(keyPtr)); [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [self length]; size_t bufferSize = dataLength + kCCBlockSizeAES128; void *buffer = malloc(bufferSize); size_t numBytesEncrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode, keyPtr, kCCBlockSizeAES128, NULL, [self bytes], dataLength, buffer, bufferSize, &numBytesEncrypted); if (cryptStatus == kCCSuccess) { return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted]; } free(buffer); return nil; } - (NSData *)AES256DecryptWithKey:(NSString *)key { char keyPtr[kCCKeySizeAES256+1]; bzero(keyPtr, sizeof(keyPtr)); [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [self length]; size_t bufferSize = dataLength + kCCBlockSizeAES128; void *buffer = malloc(bufferSize); size_t numBytesDecrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode, keyPtr, kCCBlockSizeAES128, NULL, [self bytes], dataLength, buffer, bufferSize, &numBytesDecrypted); if (cryptStatus == kCCSuccess) { return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted]; } free(buffer); return nil; } - (NSString *)newStringInBase64FromData { NSMutableString *dest = [[NSMutableString alloc] initWithString:@""]; unsigned char * working = (unsigned char *)[self bytes]; int srcLen = [self length]; for (int i=0; i<srcLen; i += 3) { for (int nib=0; nib<4; nib++) { int byt = (nib == 0)?0:nib-1; int ix = (nib+1)*2; if (i+byt >= srcLen) break; unsigned char curr = ((working[i+byt] << (8-ix)) & 0x3F); if (i+nib < srcLen) curr |= ((working[i+nib] >> ix) & 0x3F); [dest appendFormat:@"%c", base64[curr]]; } } return dest; } @end