编码和解码及MD5加密.....

常在一些网站源码中看到&#x开头的内容，这是转化成unicode编码后的汉字。

--------------------------------------------unicode编码后的汉字(呵呵)转化成中文(呵呵)---------------------------------------

step1：unicode解码(呵呵 ---------------- u5475u5475)

+(NSString *)change:(NSString *)str
{
    NSString *changeStr = @"";
    if (!str||[str isEqualToString:@""]) {
        return @"";
    }
    changeStr = [str stringByReplacingOccurrencesOfString:@"&#x" withString:@"\u"];
    changeStr = [changeStr stringByReplacingOccurrencesOfString:@";" withString:@""];
    return changeStr;
}

step2：unicode转UTF-8(u5475u5475  ---------------- 呵呵)

+(NSString *) unicodeToUtf8:(NSString *)string
{
    
    NSString *tempStr1 = [string stringByReplacingOccurrencesOfString:@"\u" withString:@"\U"];
    
    NSString *tempStr2 = [tempStr1 stringByReplacingOccurrencesOfString:@""" withString:@"\""];
    
    NSString *tempStr3 = [[@""" stringByAppendingString:tempStr2] stringByAppendingString:@"""];
    
    NSData *tempData = [tempStr3 dataUsingEncoding:NSUTF8StringEncoding];
    
    NSString* returnStr = [NSPropertyListSerialization propertyListFromData:tempData
                           
                                                           mutabilityOption:NSPropertyListImmutable
                           
                                                                     format:NULL
                           
                                                           errorDescription:NULL];
    
    return [returnStr stringByReplacingOccurrencesOfString:@"\r\n" withString:@"
"];
}

 ------------------------------------------------------------UrlEncode--------------------------------------------------

对UTF-8中文UrlEncode编码（呵呵------------------------%e5%91%b5%e5%91%b5）

- (NSString *)URLEncodedString
{
    NSString *encodedString = (NSString *)
    CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
                                            (CFStringRef)self,
                                            (CFStringRef)@"!$&'()*+,-./:;=?@_~%#[]",
                                            NULL,
                                            kCFStringEncodingUTF8);
    return encodedString;
}

- (NSString*)URLDecodedString
{
    NSString *result = ( NSString *)
    CFBridgingRelease(CFURLCreateStringByReplacingPercentEscapesUsingEncoding(kCFAllocatorDefault,
                                                                              (CFStringRef)self,
                                                                              CFSTR(""),
                                                                              kCFStringEncodingUTF8));
    return result;
}

对gb2312中文UrlEncode编码（呵呵-----------------------%ba%c7%ba%c7）

MD5加密

#import "CommonCrypto/CommonDigest.h"
@implementation MD5
+(NSString *) md5: (NSString *) inPutText
{
    const char *cStr = [inPutText UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    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]
             ] lowercaseString];
}
+(NSString *) MD5: (NSString *) inPutText
{
    const char *cStr = [inPutText UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    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]
             ] uppercaseString];
}

 .

#import <CommonCrypto/CommonDigest.h>

//生成随机guid串  （全球唯一标识符）
- (NSString *)getUniqueStrByUUID
{
    CFUUIDRef    uuidObj = CFUUIDCreate(nil);//create a new UUID
    
    //get the string representation of the UUID
    
    NSString    *uuidString = (__bridge_transfer NSString *)CFUUIDCreateString(nil, uuidObj);
    
    CFRelease(uuidObj);
    
    return uuidString ;
    
}

////获取系统当前的时间戳    (*1000代表毫秒级)
-(NSString *)getTimeInterval{
    UInt64 recordTime = [[NSDate date] timeIntervalSince1970]*1000;
    return [NSString stringWithFormat:@"%llu",recordTime];
}

//sha1（安全哈希算法）
- (NSString *)sha1:(NSString *)input
{
    const char *cstr = [input cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:input.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;
}

 对称加密代表AES，NSData进行AES加密的扩展，Key是和后台约定的key。

#import <CommonCrypto/CommonCryptor.h>

@implementation NSData (SDK_Encrypt)


- (NSData *)sdk_AESEncryptWithKey:(NSString *)key
{
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256]; // 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);

    char iv[kCCKeySizeAES128];
    bzero(iv, sizeof(iv));

    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
        keyPtr, kCCKeySizeAES256,
        iv /* 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 *)sdk_AESDecryptWithKey:(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);

    char iv[kCCKeySizeAES128];
    bzero(iv, sizeof(iv));

    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
        keyPtr, kCCKeySizeAES256,
        iv /* 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;
}

@end

 RSA加密解密相关：

需要证书文件（*.der）及p12文件（需记录密码）

公钥的作用加密，私钥的作用解密。

http://www.jianshu.com/p/2927ca2b3719

http://witcheryne.iteye.com/blog/2171850