NSData+AES.h 文件

#import <Foundation/Foundation.h>

@interface NSData (AES)

/**
 * Encrypt NSData using AES256 with a given symmetric encryption key.
 * @param key The symmetric encryption key
 */
- (NSData *)AES256EncryptWithKey:(NSString *)key;

/**
 * Decrypt NSData using AES256 with a given symmetric encryption key.
 * @param key The symmetric encryption key
 */
- (NSData *)AES256DecryptWithKey:(NSString *)key;

NSData+AES.m 文件

#import "NSData+AES.h"
#import <CommonCrypto/CommonCrypto.h>

@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;
}

@end

加密解密

    NSString *key = @"key";
    NSString *secret = @"text to encrypt";
    //加密
    NSData *plain = [secret dataUsingEncoding:NSUTF8StringEncoding];
    NSData *cipher = [plain AES256EncryptWithKey:key];
    
    printf("%s\n", [[cipher description] UTF8String]);
    NSLog(@"%@", [[NSString alloc] initWithData:cipher encoding:NSUTF8StringEncoding]);//打印出null,这是因为没有解密。
    
    //解密
    plain = [cipher AES256DecryptWithKey:key];
    printf("%s\n", [[plain description] UTF8String]);
    NSLog(@"%@", [[NSString alloc] initWithData:plain encoding:NSUTF8StringEncoding]);