关于AES加密（下）

上期提供了Java中AES加密，因为在使用时，一般Java作为服务器或者终端，可能涉及到ios作为终端，至少我遇到的场景是这样的，所以贴上IOS端的AES加密。首先我下面的代码是基于NSData的Category；上代码吧：

NSData+AES256.h

#import 
#import 
#import 
@interface NSData (AES256)
+ (NSData *)AES256EncryptWithPlainText:(NSString *)plain;        /*加密方法,参数需要加密的内容*/
+ (NSData *)AES256DecryptWithCiphertext:(NSString *)ciphertexts; /*解密方法，参数数密文*/
@end

NSData+AES256.m

#import "NSData+AES256.h"
#define PASSWORD @"Per vallum duces Labant"

static const char encodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const NSUInteger kAlgorithmKeySize = kCCKeySizeAES256;
const NSUInteger kPBKDFRounds = 10000;  // ~80ms on an iPhone 4

//static Byte saltBuff[] = {0,1,2,3,4,5,6,7,8,9,0xA,0xB,0xC,0xD,0xE,0xF};

static NSString *key = @"H@}+T@b}hS/5798DGILXURXp'o$cC%!XpOibP N6Gg@1um*kAS; [7y&BcSSo+m*";

static Byte ivBuff[]   = {0xA,1,0xB,5,4,0xF,7,9,0x17,3,1,6,8,0xC,0xD,91};

@implementation NSData (AES256)


+ (NSData *)AESKeyForPassword:(NSString *)password{                  //Derive a key from a text password/passphrase
    
    NSMutableData *derivedKey = [NSMutableData dataWithLength:kAlgorithmKeySize];
    
    //NSData *salt = [NSData dataWithBytes:saltBuff length:kCCKeySizeAES128];
    
    NSData *salt = [key dataUsingEncoding:NSUTF8StringEncoding];
    
    int result = CCKeyDerivationPBKDF(kCCPBKDF2,        // algorithm算法
                                  password.UTF8String,  // password密码
                                  password.length,      // passwordLength密码的长度
                                  salt.bytes,           // salt内容
                                  salt.length,          // saltLen长度
                                  kCCPRFHmacAlgSHA1,    // PRF
                                  kPBKDFRounds,         // rounds循环次数
                                  derivedKey.mutableBytes, // derivedKey
                                  derivedKey.length);   // derivedKeyLen derive:出自
    
    NSAssert(result == kCCSuccess,
             @"Unable to create AES key for spassword: %d", result);
    return derivedKey;
}

/*加密方法*/
+ (NSData*)AES256EncryptWithPlainText:(NSString *)plain {
    NSData *plainText = [plain dataUsingEncoding:NSUTF8StringEncoding];
	// '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)
        
	NSUInteger dataLength = [plainText length];

	size_t bufferSize = dataLength + kCCBlockSizeAES128;
	void *buffer = malloc(bufferSize);
    bzero(buffer, sizeof(buffer));
	
	size_t numBytesEncrypted = 0;
    
	CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,kCCOptionPKCS7Padding,
                                          [[NSData AESKeyForPassword:PASSWORD] bytes], kCCKeySizeAES256,
										  ivBuff /* initialization vector (optional) */,
										  [plainText bytes], dataLength, /* input */
										  buffer, bufferSize, /* output */
										  &numBytesEncrypted);
	if (cryptStatus == kCCSuccess) {
        NSData *encryptData = [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
        NSLog(@"%@", [encryptData base64Encoding]);
		return encryptData;
	}
	
	free(buffer); //free the buffer;
	return nil;
}

/*解密方法*/
+ (NSData *)AES256DecryptWithCiphertext:(NSString *)ciphertexts{
    
    NSData *cipherData = [NSData dataWithBase64EncodedString:ciphertexts];
	// '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)
	    
	NSUInteger dataLength = [cipherData length];
	
	size_t bufferSize = dataLength + kCCBlockSizeAES128;
	void *buffer = malloc(bufferSize);
	    
	size_t numBytesDecrypted = 0;
	CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
										  [[NSData AESKeyForPassword:PASSWORD] bytes], kCCKeySizeAES256,
										  ivBuff ,/* initialization vector (optional) */
										  [cipherData bytes], dataLength, /* input */
										  buffer, bufferSize, /* output */
										  &numBytesDecrypted);
	
	if (cryptStatus == kCCSuccess) {
        NSData *encryptData = [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
		return encryptData;
	}
	
	free(buffer); //free the buffer;
	return nil;
}

+ (id)dataWithBase64EncodedString:(NSString *)string;
{
    if (string == nil)
        [NSException raise:NSInvalidArgumentException format:nil];
    if ([string length] == 0)
        return [NSData data];
    
    static char *decodingTable = NULL;
    if (decodingTable == NULL)
    {
        decodingTable = malloc(256);
        if (decodingTable == NULL)
            return nil;
        memset(decodingTable, CHAR_MAX, 256);
        NSUInteger i;
        for (i = 0; i < 64; i++)
            decodingTable[(short)encodingTable[i]] = i;
    }
    
    const char *characters = [string cStringUsingEncoding:NSASCIIStringEncoding];
    if (characters == NULL)     //  Not an ASCII string!
        return nil;
    char *bytes = malloc((([string length] + 3) / 4) * 3);
    if (bytes == NULL)
        return nil;
    NSUInteger length = 0;
    
    NSUInteger i = 0;
    while (YES)
    {
        char buffer[4];
        short bufferLength;
        for (bufferLength = 0; bufferLength < 4; i++)
        {
            if (characters[i] == '\0')
                break;
            if (isspace(characters[i]) || characters[i] == '=')
                continue;
            buffer[bufferLength] = decodingTable[(short)characters[i]];
            if (buffer[bufferLength++] == CHAR_MAX)      //  Illegal character!
            {
                free(bytes);
                return nil;
            }
        }
        
        if (bufferLength == 0)
            break;
        if (bufferLength == 1)      //  At least two characters are needed to produce one byte!
        {
            free(bytes);
            return nil;
        }
        
        //  Decode the characters in the buffer to bytes.
        bytes[length++] = (buffer[0] << 2) | (buffer[1] >> 4);
        if (bufferLength > 2)
            bytes[length++] = (buffer[1] << 4) | (buffer[2] >> 2);
        if (bufferLength > 3)
            bytes[length++] = (buffer[2] << 6) | buffer[3];
    }
    
    bytes = realloc(bytes, length);
    return [NSData dataWithBytesNoCopy:bytes length:length];
}

- (NSString *)base64Encoding;
{
    if ([self length] == 0)
        return @"";
    
    char *characters = malloc((([self length] + 2) / 3) * 4);
    if (characters == NULL)
        return nil;
    NSUInteger length = 0;
    
    NSUInteger i = 0;
    while (i < [self length])
    {
        char buffer[3] = {0,0,0};
        short bufferLength = 0;
        while (bufferLength < 3 && i < [self length])
            buffer[bufferLength++] = ((char *)[self bytes])[i++];
        
        //  Encode the bytes in the buffer to four characters, including padding "=" characters if necessary.
        characters[length++] = encodingTable[(buffer[0] & 0xFC) >> 2];
        characters[length++] = encodingTable[((buffer[0] & 0x03) << 4) | ((buffer[1] & 0xF0) >> 4)];
        if (bufferLength > 1)
            characters[length++] = encodingTable[((buffer[1] & 0x0F) << 2) | ((buffer[2] & 0xC0) >> 6)];
        else characters[length++] = '=';
        if (bufferLength > 2)
            characters[length++] = encodingTable[buffer[2] & 0x3F];
        else characters[length++] = '=';    
    }
    
    return [[[NSString alloc] initWithBytesNoCopy:characters length:length encoding:NSASCIIStringEncoding freeWhenDone:YES] autorelease];
}
@end