iOS-AES对称加密

实验要求

编程语言不限制
明文“学号+姓名+专业+学院”
实现对明文的加密，输出密文
对密文实现解密，输出明文
不能是DES加密算法
报告中说明该语言提供的加密函数都有哪些，具体的使用方法并分析优缺点

代码

#import "ViewController.h"
#import "AES.h"
#import "NSString+AES.h"


@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    //原文信息
    NSString *plainText = @"3180807001+黄振锋+计算机科学与技术+网络空间安全学院";
    //秘钥
    NSString *key = @"HuangZhenFeng";
    NSLog(@"纯加密:%@",[plainText AES256_Encrypt:key]);
    NSLog(@"纯解密:%@",[[plainText AES256_Encrypt:key] AES256_Decrypt:key]);

    //原文转码数据NSData
    NSData *plainData = [plainText dataUsingEncoding:NSUTF8StringEncoding];
    //用秘钥加密
    NSData *cipher = [plainData AES256EncryptWithKey:key];
    //得到密文
    NSLog(@"密文:%@",[cipher base64EncodedStringWithOptions:0]);
    
    //用秘钥解密
    NSData *cipher1 = [cipher AES256DecryptWithKey:key];
    //得到明文
    NSString *plainText1 = [[NSString alloc] initWithData:cipher1 encoding:NSUTF8StringEncoding];
    NSLog(@"明文:%@",plainText1);
}
#import "AES.h"
#import <Foundation/Foundation.h>
#import <CommonCrypto/CommonCryptor.h>

static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

@implementation NSData (AES)

- (NSData *)AES256EncryptWithKey:(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);
    
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* 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 *)AES256DecryptWithKey:(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);
    
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* 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;
}


- (NSString *)newStringInBase64FromData            //追加64编码
{
    NSMutableString *dest = [[NSMutableString alloc] initWithString:@""];
    unsigned char * working = (unsigned char *)[self bytes];
    int srcLen = [self length];
    for (int i=0; i<srcLen; i += 3) {
        for (int nib=0; nib<4; nib++) {
            int byt = (nib == 0)?0:nib-1;
            int ix = (nib+1)*2;
            if (i+byt >= srcLen) break;
            unsigned char curr = ((working[i+byt] << (8-ix)) & 0x3F);
            if (i+nib < srcLen) curr |= ((working[i+nib] >> ix) & 0x3F);
            [dest appendFormat:@"%c", base64[curr]];
        }
    }
    return dest;
}

+ (NSString*)base64encode:(NSString*)str
{
    if ([str length] == 0)
        return @"";
    const char *source = [str UTF8String];
    int strlength  = strlen(source);
    char *characters = malloc(((strlength + 2) / 3) * 4);
    if (characters == NULL)
        return nil;
    NSUInteger length = 0;
    NSUInteger i = 0;
    while (i < strlength) {
        char buffer[3] = {0,0,0};
        short bufferLength = 0;
        while (bufferLength < 3 && i < strlength)
            buffer[bufferLength++] = source[i++];
        characters[length++] = base64[(buffer[0] & 0xFC) >> 2];
        characters[length++] = base64[((buffer[0] & 0x03) << 4) | ((buffer[1] & 0xF0) >> 4)];
        if (bufferLength > 1)
            characters[length++] = base64[((buffer[1] & 0x0F) << 2) | ((buffer[2] & 0xC0) >> 6)];
        else characters[length++] = '=';
        if (bufferLength > 2)
            characters[length++] = base64[buffer[2] & 0x3F];
        else characters[length++] = '=';
    }
    NSString *g = [[NSString alloc] initWithBytesNoCopy:characters length:length encoding:NSASCIIStringEncoding freeWhenDone:YES];
    return g;
}
#import "NSData+AES.h"

@implementation NSData (AES)

//加密
- (NSData *) AES256_Encrypt:(NSString *)key{
    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;
}
//解密
- (NSData *) AES256_Decrypt:(NSString *)key{
    
    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;
}
#import "NSString+AES.h"

@implementation NSString (AES)

//加密
- (NSString *) AES256_Encrypt:(NSString *)key{
    const char *cstr = [self cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:self.length];
    //对数据进行加密
    NSData *result = [data AES256_Encrypt:key];
    
    //转换为2进制字符串
    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;
}
//解密
- (NSString *) AES256_Decrypt:(NSString *)key{
    //转换为2进制Data
    NSMutableData *data = [NSMutableData dataWithCapacity:self.length / 2];
    unsigned char whole_byte;
    char byte_chars[3] = {'\0','\0','\0'};
    int i;
    for (i=0; i < [self length] / 2; i++) {
        byte_chars[0] = [self characterAtIndex:i*2];
        byte_chars[1] = [self characterAtIndex:i*2+1];
        whole_byte = strtol(byte_chars, NULL, 16);
        [data appendBytes:&whole_byte length:1];
    }
    //对数据进行解密
    NSData* result = [data AES256_Decrypt:key];
    if (result && result.length > 0) {
        return [[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding];
    }
    return nil;}

iOS-AES对称加密

总结

常见的对称加密算法有DES、3DES、AES。
本次实验使用对称加密算法是AES，AES是高级加密，也是目前使用最多的对称加密算法，目前美国国家安全局使用AES加密，苹果的钥匙串访问就是使用AES加密。对称加密的优点是算法公开，计算量小，加密速度快，加密效率高。对称加密的缺点是双方使用相同的钥匙，安全性得不到保证。使用对称加密需要注意的是秘钥的保密工作需要非常重视，并且秘钥要求定期更换。
实验中，我先使用纯AES算法加解密，然后我再使用AES+Base64算法加解密。我使用的是Objective-C语言进行编程，我先使用AES算法纯加密的时候，我发现加密方法目前不支持中文加解密，所以解密出来的东西为空，但是是数字或者英文的时候，可以加解密。后来我使用AES+Base64算法的时候，可以对中文进行正常的加解密。AES+Base64实际上是在纯AES算法上再对加密内容进行Base64加密，得到一串不含空格的英文、数字、符号的组合字符串。其中，纯AES算法加解密函数分别是：- (NSData *) AES256_Encrypt:(NSString *)key;，- (NSData *) AES256_Decrypt:(NSString *)key;。AES+Base64算法加解密函数为：- (NSData *)AES256EncryptWithKey:(NSString *)key; - (NSData *)AES256DecryptWithKey:(NSString *)key; - (NSString *)newStringInBase64FromData;。其中key是自定义的秘钥，我的秘钥设定为“HuangZhenFeng”，明文不需要用参数传递进入，因为Objective-C支持在函数里面使用“self”来提取谁调用这个函数，所以就能取到原文信息。