IOS開發各種加解密，編解碼

1.AES加解密，給NSData添加類別 NSData+AES
添加頭文件#import

- (NSData *)AES256EncryptWithKey:(NSString *)key {//加密

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 {//解密
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;
}

2.base64編解碼參考
GTMDefines.h
GTMBase64.h
GTMBase64.m
代碼下載地址：http://download.csdn.net/detail/u014063717/9516591

3.各種加密，數字摘要。給NSString添加類別NSString+Encrypto
（1）.MD5數字摘要

- (NSString *)md5 {

const char *cStr = [self UTF8String];
unsigned char result[16];
CC_MD5( cStr, strlen(cStr), result );
return [NSString stringWithFormat:@%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X,
result[0], result[1], result[2], result[3],
result[4], result[5], result[6], result[7],
result[8], result[9], result[10], result[11],
result[12], result[13], result[14], result[15]
];
}

（2）SHA1摘要

- (NSString*) sha1
{
    const char *cstr = [self cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:self.length];

    uint8_t digest[CC_SHA1_DIGEST_LENGTH];

    CC_SHA1(data.bytes, data.length, digest);

    NSMutableString* output = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH * 2];

    for(int i = 0; i < CC_SHA1_DIGEST_LENGTH; i++)
        [output appendFormat:@%02x, digest[i]];

    return output;
}

（3）base64編碼

- (NSString *) base64
{    
    NSData * data = [self dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]; 
    data = [GTMBase64 encodeData:data]; 
    NSString * output = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]; 
    return output; 
}

（4）SHA1與base64結合

- (NSString *) sha1_base64
{
    const char *cstr = [self cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:self.length];

    uint8_t digest[CC_SHA1_DIGEST_LENGTH];

    CC_SHA1(data.bytes, data.length, digest);

    NSData * base64 = [[NSData alloc]initWithBytes:digest length:CC_SHA1_DIGEST_LENGTH];
    base64 = [GTMBase64 encodeData:base64];

    NSString * output = [[NSString alloc] initWithData:base64 encoding:NSUTF8StringEncoding]; 
    return output; 
}

（5）MD5與base64結合

- (NSString *) md5_base64
{
    const char *cStr = [self UTF8String];
    unsigned char digest[CC_MD5_DIGEST_LENGTH];
    CC_MD5( cStr, strlen(cStr), digest );

    NSData * base64 = [[NSData alloc]initWithBytes:digest length:CC_MD5_DIGEST_LENGTH];
    base64 = [GTMBase64 encodeData:base64];

    NSString * output = [[NSString alloc] initWithData:base64 encoding:NSUTF8StringEncoding]; 
    return output;
}

4.3DES是一種對稱的加密方式，因爲用的同一個密鑰。

對於加解密的安全性什麼大家可以google，baidu自己找資料參考。

我也不過是簡單的說一下通信加密中的一種可實現方案而已。

同樣的3DES加密基本也都是統一的，系統也直接提供了API，基本代碼如下

//3des加解密
+ (NSString*)TripleDES:(NSString*)plainText encryptOrDecrypt:(CCOperation)encryptOrDecrypt
{
const void *vplainText;
size_t plainTextBufferSize;

if (encryptOrDecrypt == kCCDecrypt)//解密
{
NSData *EncryptData = [GTMBase64 decodeData:[plainText dataUsingEncoding:NSUTF8StringEncoding]];
plainTextBufferSize = [EncryptData length];
vplainText = [EncryptData bytes];
}
else //加密
{
NSData* data = [plainText dataUsingEncoding:NSUTF8StringEncoding];
plainTextBufferSize = [data length];
vplainText = (const void *)[data bytes];
}

CCCryptorStatus ccStatus;
uint8_t *bufferPtr = NULL;
size_t bufferPtrSize = 0;
size_t movedBytes = 0;

bufferPtrSize = (plainTextBufferSize + kCCBlockSize3DES) & ~(kCCBlockSize3DES - 1);
bufferPtr = malloc( bufferPtrSize * sizeof(uint8_t));
memset((void *)bufferPtr, 0x0, bufferPtrSize);
// memset((void *) iv, 0x0, (size_t) sizeof(iv));

const void *vkey = (const void *) [DESKEY UTF8String];
// NSString *initVec = @init Vec;
//const void *vinitVec = (const void *) [initVec UTF8String];
// Byte iv[] = {0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF};
ccStatus = CCCrypt(encryptOrDecrypt,
kCCAlgorithm3DES,
kCCOptionPKCS7Padding | kCCOptionECBMode,
vkey,
kCCKeySize3DES,
nil,
vplainText,
plainTextBufferSize,
(void *)bufferPtr,
bufferPtrSize,
&movedBytes);
//if (ccStatus == kCCSuccess) NSLog(@SUCCESS);
/*else if (ccStatus == kCC ParamError) return @PARAM ERROR;
else if (ccStatus == kCCBufferTooSmall) return @BUFFER TOO SMALL;
else if (ccStatus == kCCMemoryFailure) return @MEMORY FAILURE;
else if (ccStatus == kCCAlignmentError) return @ALIGNMENT;
else if (ccStatus == kCCDecodeError) return @DECODE ERROR;
else if (ccStatus == kCCUnimplemented) return @UNIMPLEMENTED; */

NSString *result;

if (encryptOrDecrypt == kCCDecrypt)
{
result = [[[NSString alloc] initWithData:[NSData dataWithBytes:(const void *)bufferPtr
length:(NSUInteger)movedBytes]
encoding:NSUTF8StringEncoding]
autorelease];
}
else
{
NSData *myData = [NSData dataWithBytes:(const void *)bufferPtr length:(NSUInteger)movedBytes];
result = [GTMBase64 stringByEncodingData:myData];
}

return result;
}