BASE64转换，内含:IOS自带DES加解密

最近项目需要保密，于是乎小小研究了一下，发现苹果自带密码库，不错！

//引入IOS自带密码库
#import <CommonCrypto/CommonCryptor.h>

IOS支持的加解密算法如下

enum {
kCCAlgorithmAES128 = 0,
kCCAlgorithmDES,
kCCAlgorithm3DES,
kCCAlgorithmCAST,
kCCAlgorithmRC4,
kCCAlgorithmRC2,
kCCAlgorithmBlowfish
};
typedef uint32_t CCAlgorithm;

其中前4个位DES/ADES，后两个位RSA，DES/ADES加解密使用相同的key，RSA使用公钥加密、私钥解密。

我就介绍下，把文本转换成为BASE64格式字符串后，再进行DES加密、解密，把BASE64格式字符串转换为文本的过程。

为了调用起来方便，我建立了转换宏

#define __BASE64( text )        [CommonFunc base64StringFromText:text]
#define __TEXT( base64 )        [CommonFunc textFromBase64String:base64]

文本与BASE64格式字符串转换实现如下:

/******************************************************************************
函数名称 : + (NSData *)dataWithBase64EncodedString:(NSString *)string
函数描述 : base64格式字符串转换为文本数据
输入参数 : (NSString *)string
输出参数 : N/A
返回参数 : (NSData *)
备注信息 :
******************************************************************************/
+ (NSData *)dataWithBase64EncodedString:(NSString *)string
{
if (string == nil)
[NSException raise:NSInvalidArgumentException format:nil];
if ([string length] == 0)
return [NSData data];

static char *decodingTable = NULL;
if (decodingTable == NULL)
{
decodingTable = malloc(256);
if (decodingTable == NULL)
return nil;
memset(decodingTable, CHAR_MAX, 256);
NSUInteger i;
for (i = 0; i < 64; i++)
decodingTable[(short)encodingTable[i]] = i;
}

const char *characters = [string cStringUsingEncoding:NSASCIIStringEncoding];
if (characters == NULL)     //  Not an ASCII string!
return nil;
char *bytes = malloc((([string length] + 3) / 4) * 3);
if (bytes == NULL)
return nil;
NSUInteger length = 0;

NSUInteger i = 0;
while (YES)
{
char buffer[4];
short bufferLength;
for (bufferLength = 0; bufferLength < 4; i++)
{
if (characters[i] == '\0')
break;
if (isspace(characters[i]) || characters[i] == '=')
continue;
buffer[bufferLength] = decodingTable[(short)characters[i]];
if (buffer[bufferLength++] == CHAR_MAX)      //  Illegal character!
{
free(bytes);
return nil;
}
}

if (bufferLength == 0)
break;
if (bufferLength == 1)      //  At least two characters are needed to produce one byte!
{
free(bytes);
return nil;
}

//  Decode the characters in the buffer to bytes.
bytes[length++] = (buffer[0] << 2) | (buffer[1] >> 4);
if (bufferLength > 2)
bytes[length++] = (buffer[1] << 4) | (buffer[2] >> 2);
if (bufferLength > 3)
bytes[length++] = (buffer[2] << 6) | buffer[3];
}

bytes = realloc(bytes, length);
return [NSData dataWithBytesNoCopy:bytes length:length];
}

/******************************************************************************
函数名称 : + (NSString *)base64EncodedStringFrom:(NSData *)data
函数描述 : 文本数据转换为base64格式字符串
输入参数 : (NSData *)data
输出参数 : N/A
返回参数 : (NSString *)
备注信息 :
******************************************************************************/
+ (NSString *)base64EncodedStringFrom:(NSData *)data
{
if ([data length] == 0)
return @"";

char *characters = malloc((([data length] + 2) / 3) * 4);
if (characters == NULL)
return nil;
NSUInteger length = 0;

NSUInteger i = 0;
while (i < [data length])
{
char buffer[3] = {0,0,0};
short bufferLength = 0;
while (bufferLength < 3 && i < [data length])
buffer[bufferLength++] = ((char *)[data bytes])[i++];

//  Encode the bytes in the buffer to four characters, including padding "=" characters if necessary.
characters[length++] = encodingTable[(buffer[0] & 0xFC) >> 2];
characters[length++] = encodingTable[((buffer[0] & 0x03) << 4) | ((buffer[1] & 0xF0) >> 4)];
if (bufferLength > 1)
characters[length++] = encodingTable[((buffer[1] & 0x0F) << 2) | ((buffer[2] & 0xC0) >> 6)];
else characters[length++] = '=';
if (bufferLength > 2)
characters[length++] = encodingTable[buffer[2] & 0x3F];
else characters[length++] = '=';
}

return [[NSString alloc] initWithBytesNoCopy:characters length:length encoding:NSASCIIStringEncoding freeWhenDone:YES];
}

DES加密、解密实现如下:

/******************************************************************************
函数名称 : + (NSData *)DESEncrypt:(NSData *)data WithKey:(NSString *)key
函数描述 : 文本数据进行DES加密
输入参数 : (NSData *)data
(NSString *)key
输出参数 : N/A
返回参数 : (NSData *)
备注信息 : 此函数不可用于过长文本
******************************************************************************/
+ (NSData *)DESEncrypt:(NSData *)data WithKey:(NSString *)key
{
char keyPtr[kCCKeySizeAES256+1];
bzero(keyPtr, sizeof(keyPtr));

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

NSUInteger dataLength = [data length];

size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(bufferSize);

size_t numBytesEncrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmDES,
kCCOptionPKCS7Padding | kCCOptionECBMode,
keyPtr, kCCBlockSizeDES,
NULL,
[data bytes], dataLength,
buffer, bufferSize,
&numBytesEncrypted);
if (cryptStatus == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
}

free(buffer);
return nil;
}

/******************************************************************************
函数名称 : + (NSData *)DESEncrypt:(NSData *)data WithKey:(NSString *)key
函数描述 : 文本数据进行DES解密
输入参数 : (NSData *)data
(NSString *)key
输出参数 : N/A
返回参数 : (NSData *)
备注信息 : 此函数不可用于过长文本
******************************************************************************/
+ (NSData *)DESDecrypt:(NSData *)data WithKey:(NSString *)key
{
char keyPtr[kCCKeySizeAES256+1];
bzero(keyPtr, sizeof(keyPtr));

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

NSUInteger dataLength = [data length];

size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(bufferSize);

size_t numBytesDecrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmDES,
kCCOptionPKCS7Padding | kCCOptionECBMode,
keyPtr, kCCBlockSizeDES,
NULL,
[data bytes], dataLength,
buffer, bufferSize,
&numBytesDecrypted);

if (cryptStatus == kCCSuccess) {
return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
}

free(buffer);
return nil;
}

然后把两者结合起来使用，我认为更加安全，于是我就这样做了:

+ (NSString *)base64StringFromText:(NSString *)text
{
if (text && ![text isEqualToString:LocalStr_None]) {
//取项目的bundleIdentifier作为KEY
NSString *key = [[NSBundle mainBundle] bundleIdentifier];
NSData *data = [text dataUsingEncoding:NSUTF8StringEncoding];
//IOS 自带DES加密 Begin
data = [self DESEncrypt:data WithKey:key];
//IOS 自带DES加密 End
return [self base64EncodedStringFrom:data];
}
else {
return LocalStr_None;
}
}

+ (NSString *)textFromBase64String:(NSString *)base64
{
if (base64 && ![base64 isEqualToString:LocalStr_None]) {
//取项目的bundleIdentifier作为KEY
NSString *key = [[NSBundle mainBundle] bundleIdentifier];
NSData *data = [self dataWithBase64EncodedString:base64];
//IOS 自带DES解密 Begin
data = [self DESDecrypt:data WithKey:key];
//IOS 自带DES加密 End
return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
}
else {
return LocalStr_None;
}
}

还没看懂？ 没关系，来看图，看例子







PRJ_base64.zip 例子下载地址:http://ishare.iask.sina.com.cn/f/34862560.html