AES加密初探

最近在整一個密碼鍵盤的加密，第一次涉及到AES這種加密方式，在這裏總結一下：

話很少說，直接上代碼
.h
import <Foundation/Foundation.h>

@interface LanAES : NSObject
+(NSData *)AES256ParmEncryptWithKey:(NSString *)key Encrypttext:(NSData *)text;   //加密
+(NSData *)AES256ParmDecryptWithKey:(NSString *)key Decrypttext:(NSData *)text;   //解密
+(NSString *) aes256_encrypt:(NSString *)key Encrypttext:(NSString *)text;
+(NSString *) aes256_decrypt:(NSString *)key Decrypttext:(NSString *)text;

@end


.m

#import "LanAES.h"
#import <CommonCrypto/CommonCryptor.h>

@implementation LanAES
+(NSData *)AES256ParmEncryptWithKey:(NSString *)key Encrypttext:(NSData *)text  //加密
{
    char keyPtr[kCCKeySizeAES256+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    NSUInteger dataLength = [text length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding | kCCOptionECBMode,
                                          keyPtr, kCCBlockSizeAES128,
                                          NULL,
                                          [text bytes], dataLength,
                                          buffer, bufferSize,
                                          &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    free(buffer);
    return nil;
}

+ (NSData *)AES256ParmDecryptWithKey:(NSString *)key Decrypttext:(NSData *)text  //解密
{
    char keyPtr[kCCKeySizeAES256+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    NSUInteger dataLength = [text length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding | kCCOptionECBMode,
                                          keyPtr, kCCBlockSizeAES128,
                                          NULL,
                                          [text bytes], dataLength,
                                          buffer, bufferSize,
                                          &numBytesDecrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
    }
    free(buffer);
    return nil;
}

+(NSString *) aes256_encrypt:(NSString *)key Encrypttext:(NSString *)text
{
    const char *cstr = [text cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:text.length];
    //對數據進行加密
    NSData *result = [LanAES AES256ParmEncryptWithKey:key Encrypttext:data];
    
    //轉換爲2進制字符串
    if (result && result.length > 0) {
        
        Byte *datas = (Byte*)[result bytes];
        NSMutableString *output = [NSMutableString stringWithCapacity:result.length * 2];
        for(int i = 0; i < result.length; i++){
            [output appendFormat:@"%02x", datas[i]];
        }
        return output;
    }
    return nil;
}

+(NSString *) aes256_decrypt:(NSString *)key Decrypttext:(NSString *)text
{
    //轉換爲2進制Data
    NSMutableData *data = [NSMutableData dataWithCapacity:text.length / 2];
    unsigned char whole_byte;
    char byte_chars[3] = {'\0','\0','\0'};
    int i;
    for (i=0; i < [text length] / 2; i++) {
        byte_chars[0] = [text characterAtIndex:i*2];
        byte_chars[1] = [text characterAtIndex:i*2+1];
        whole_byte = strtol(byte_chars, NULL, 16);
        [data appendBytes:&whole_byte length:1];
    }
    
    //對數據進行解密
    NSData* result = [LanAES  AES256ParmDecryptWithKey:key Decrypttext:data];
    if (result && result.length > 0) {
        return [[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding];
    }
    return nil;
}

 分組密碼有五種工做體制：1.電碼本模式（Electronic Codebook Book (ECB)）；2.密碼分組連接模式（Cipher Block Chaining (CBC)）；3.計算器模式（Counter (CTR)）；4.密碼反饋模式（Cipher FeedBack (CFB)）；5.輸出反饋模式（Output FeedBack (OFB)）。

參考

http://www.cnblogs.com/starwolf/p/3365834.html

 

http://blog.csdn.net/lanzeng_in_sz/article/details/50218683