iOS 自定义加密算法

开发中除了常见的RSA加密、MD5加密等，可以实现自动以算法配合加密方法使用，代码如下:

// 自定义加密算法
+ (NSString *)archlyEncryptionAlgorithmWithData:(NSString *)data key:(NSString *)key isDecode:(BOOL)isDecode{
    int len = 128;
    
    if (key == nil || key.length == 0) {
        key = @"";
    }
    
    if (data.length < 1) {
        return @"";
    }
    
    NSString *md5Key = [key md5Hash];
    NSString *keyA = [[md5Key substringToIndex:16] md5Hash];
    NSString *keyB = [[md5Key substringFromIndex:16] md5Hash];
    NSString *keyC;
    if (isDecode == YES) { // 解密
        keyC = [data substringToIndex:4];
    }else{ // 加密
        NSString *nowTime = [self getNowTimeTimestampms];
        NSString *md5Time = [nowTime md5Hash];
        keyC = [md5Time substringFromIndex:md5Time.length - 4];
    }
    NSString *cryptkey = [NSString stringWithFormat:@"%@%@",keyA,[[NSString stringWithFormat:@"%@%@",keyA,keyC] md5Hash]];
    NSInteger cryptkeyLength = cryptkey.length;
    NSString *newData;
    if (isDecode == YES) { // 解密
        NSString *preparStr = [data substringFromIndex:4];
        if (preparStr.length % 4 != 0) {
            NSInteger coverLength = 4 - preparStr.length % 4;
                    for (int i = 0; i < coverLength ; i ++) {
                        preparStr = [preparStr stringByAppendingString:@"="];
                    }
        }
        newData = [preparStr base64Dencode];
        
    }else{ // 加密
        NSString *sub = [[[NSString stringWithFormat:@"%@%@",data,keyB] md5Hash] substringToIndex:16];
        newData = [NSString stringWithFormat:@"0000000000%@%@",sub,data];
    }
    NSString *result = @"";
    NSMutableArray *box = [NSMutableArray array];
    for (int i = 0; i < len; i++) {
        [box addObject:@(i)];
    }
    
    NSMutableArray *rndkArray = [NSMutableArray array];
    for (int i = 0; i < len; i ++) {
         unichar c =  [cryptkey characterAtIndex:i % cryptkeyLength];
        [rndkArray addObject:@([self ascIIToNumber:[NSString stringWithFormat:@"%C",c]])];
    }
    int j1 = 0;
    for (int i = 0; i < len; i ++) {
        int boxNum = [box[i] intValue];
        int rndkArrayNum = [rndkArray[i] intValue];
        j1 = (j1 + boxNum +rndkArrayNum) % len;
        [box exchangeObjectAtIndex:i withObjectAtIndex:j1];
    }
    
    int a2 = 0;
    int j2 = 0;
    for (int i = 0; i < newData.length; i ++) {
        a2 = (a2 +1) % len;
        int boxNum = [box[a2] intValue];
        j2 = (j2 + boxNum) % len;
        [box exchangeObjectAtIndex:a2 withObjectAtIndex:j2];
        unichar c =  [newData characterAtIndex:i];
        int ASCIIC = [self ascIIToNumber:[NSString stringWithFormat:@"%C",c]];
        
        int value = ([box[a2] intValue] + [box[j2] intValue]) % len;
        int boxValue = [box[value] intValue];
        
        int newValue = ASCIIC ^ boxValue;
        NSString *charStr = [self numberToASCII:newValue];
        result = [NSString stringWithFormat:@"%@%@",result,charStr];
    }
    
    if (isDecode == YES) { // 解密
        if (result.length < 1) {
            NSLog(@"result 为空");
            return @"";
        }
        BOOL bool1 = [[result substringToIndex:10] isEqualToString:@"0000000000"];
        BOOL bool2 = [[result substringToIndex:10] intValue] > [[self getNowTimeTimestamp] intValue];
        
        NSString *string1 = [result substringWithRange:NSMakeRange(10, 16)];
        NSString *md5Str = [[NSString stringWithFormat:@"%@%@",[result substringFromIndex:26],keyB] md5Hash];
        NSString *string2 = [md5Str substringToIndex:16];
        BOOL bool3 = [string2 isEqualToString:string1];
        if ((bool1 || bool2) && bool3) {
            return [result substringFromIndex:26];
        }else {
            return @"";
        }
        
    }else{ // 加密
        NSString *baseStr = [[result base64Encode] stringByReplacingOccurrencesOfString:@"=" withString:@""];
        return [NSString stringWithFormat:@"%@%@",keyC,baseStr];
    }
    
}

调用的辅助方法如下：
实现NSStirng 分类

- (NSString *)md5Hash {
    const char *plain = self.UTF8String;
    unsigned char *digest;
    digest = malloc(CC_MD5_DIGEST_LENGTH);
    
    CC_MD5(plain, (CC_LONG)strlen(plain), digest);
    
    NSString *encode = [self stringFromBytes:digest length:CC_MD5_DIGEST_LENGTH];
    free(digest);
    return encode;
}

#pragma mark - Bytes转字符串
/**
 字符大小写可以通过修改“%02X”中的x修改,下面采用的是大写X  小写用 x
 */
- (NSString *)stringFromBytes:(uint8_t *)bytes length:(int)length {
    NSMutableString *strM = [NSMutableString string];
    
    for (int i = 0; i < length; i++) {
        [strM appendFormat:@"%02x", bytes[i]];
    }
    
    return [strM copy];
}

// base64编码
- (NSString *)base64Encode{
    NSData * body = [self dataUsingEncoding:NSUTF8StringEncoding];
    
    return [body base64EncodedStringWithOptions:0];
}

// base64解码
- (NSString *)base64Dencode
{
    
    NSData *decodeData = [[NSData alloc] initWithBase64EncodedString:self options:0]; //解码
        
    NSString *decodeString = [[NSString alloc] initWithData:decodeData encoding:NSUTF8StringEncoding];
    
    return decodeString;
}

实例方法如下：

// 获取当前时间戳  毫秒
- (NSString *)getNowTimeTimestampms{

    NSDate *datenow = [NSDate date];

    NSString *timeSp = [NSString stringWithFormat:@"%ld", (long)([datenow timeIntervalSince1970]*1000)];
    
    return timeSp;
}

// 获取当前时间戳  秒
- (NSString *)getNowTimeTimestamp{

    NSDate *datenow = [NSDate date];

    NSString *timeSp = [NSString stringWithFormat:@"%ld", (long)[datenow timeIntervalSince1970]];

    return timeSp;

}

- (int)ascIIToNumber:(NSString *)c{
    return [c characterAtIndex:0];
}

- (NSString *)numberToASCII:(int) number{
    return [NSString stringWithFormat:@"%C",(unichar)number];
}

同一套算法实现加密解密，data为需要加密或解密字符串，key为盐值（可以为空），isDecode控制加密或解密