如何解决使用Objective C解密AES iOS
我打算在我的应用程序中实现AES加密，为此，我看了Rob Napier提供的内容丰富的教程：
这是一本很棒的书，我可以使用：p加密一些字符串
使用ROB NAPIER RNCRYPTOR类别
Nsstring * const
kRNCryptManagerErrorDomain = @"net.robnapier.RNCryptManager";
const CCAlgorithm kAlgorithm = kCCAlgorithmAES128;
const NSUInteger kAlgorithmKeySize = kCCKeySizeAES128;
const NSUInteger kAlgorithmBlockSize = kCCBlockSizeAES128;
const NSUInteger kAlgorithmIVSize = kCCBlockSizeAES128;
const NSUInteger kPBKDFSaltSize = 8;
const NSUInteger kPBKDFRounds = 10000; // ~80ms on an iPhone 4
// ===================
+ (NSData *)encryptedDataForData:(NSData *)data
password:(Nsstring *)password
iv:(NSData **)iv
salt:(NSData **)salt
error:(NSError **)error {
NSAssert(iv,@"IV must not be NULL");
NSAssert(salt,@"salt must not be NULL");
*iv = [self randomDataOfLength:kAlgorithmIVSize];
*salt = [self randomDataOfLength:kPBKDFSaltSize];
NSData *key = [self AESKeyForPassword:password salt:*salt];
size_t outLength;
NSMutableData *
cipherData = [NSMutableData dataWithLength:data.length +
kAlgorithmBlockSize];
CCCryptorStatus
result = CCCrypt(kCCEncrypt,// operation
kAlgorithm,// Algorithm
kCcoptionPKCS7Padding,// options
key.bytes,// key
key.length,// keylength
(*iv).bytes,// iv
data.bytes,// dataIn
data.length,// dataInLength,cipherData.mutableBytes,// dataOut
cipherData.length,// dataOutAvailable
&outLength); // dataOutMoved
if (result == kCCSuccess) {
cipherData.length = outLength;
}
else {
if (error) {
*error = [NSError errorWithDomain:kRNCryptManagerErrorDomain
code:result
userInfo:nil];
}
return nil;
}
return cipherData;
}
// ===================
+ (NSData *)randomDataOfLength:(size_t)length {
NSMutableData *data = [NSMutableData dataWithLength:length];
int result = SecRandomcopyBytes(kSecRandomDefault,length,data.mutableBytes);
NSAssert(result == 0,@"Unable to generate random bytes: %d",errno);
return data;
}
// ===================
// Replace this with a 10,000 hash calls if you don't have CCKeyDerivationPBKDF
+ (NSData *)AESKeyForPassword:(Nsstring *)password
salt:(NSData *)salt {
NSMutableData *
derivedKey = [NSMutableData dataWithLength:kAlgorithmKeySize];
int
result = CCKeyDerivationPBKDF(kCCPBKDF2,// algorithm
password.UTF8String,// password
[password lengthOfBytesUsingEncoding:NSUTF8StringEncoding],// passwordLength
salt.bytes,// salt
salt.length,// saltLen
kCCPRFHmacAlgSHA1,// PRF
kPBKDFRounds,// rounds
derivedKey.mutableBytes,// derivedKey
derivedKey.length); // derivedKeyLen
// Do not log password here
NSAssert(result == kCCSuccess,@"Unable to create AES key for password: %d",result);
return derivedKey;
}
但是在解密时，我无法正确解密，在这种情况下，我得到的是空值：供您参考的解密代码是：
+ (NSData*)decryptData:(NSData*)data key:(NSData*)key error:(NSError **)error
{
if (key.length != 16 && key.length != 24 && key.length != 32) {
*error = [NSError errorWithDomain:@"keyLengthError" code:-1 userInfo:nil];
return nil;
}
CCCryptorStatus ccStatus = kCCSuccess;
int ivLength = kCCBlockSizeAES128;
size_t clearBytes = 0;
NSMutableData *dataOut = [NSMutableData dataWithLength:data.length - ivLength];
NSLog(@"Data Out String Decrypt%@",dataOut);
ccStatus = CCCrypt(kCCDecrypt,kCCAlgorithmAES,kCcoptionPKCS7Padding,key.bytes,key.length,data.bytes,data.bytes + ivLength,data.length - ivLength,dataOut.mutableBytes,dataOut.length,&clearBytes);
if (ccStatus == kCCSuccess) {
dataOut.length = clearBytes;
}
else {
if (error) {
*error = [NSError errorWithDomain:@"kEncryptionError" code:ccStatus userInfo:nil];
}
dataOut = nil;
}
return dataOut;
}
在这种情况下我哪里出错了？我已经尝试了几天以解决问题。有人可以帮我吗？
解决方法
在您提到的示例中给出的方法引用了Rob Napiers Github Repo。
只需使用您提供的密码，盐等对它进行测试，就可以了！
可以理解，您想在解密时扔掉password:和iv:参数以及salt:参数，并且只使用key:。那么，您至少需要iv:才能做到这一点。但是，正如罗布（Rob）在评论您的其他问题时一样，请不要重新发明轮子。
我上面链接的方法与您要解密的参数配合得很好。与您的代码唯一的区别在于，password，iv和salt可以解密。
除了您想要开发无需密码即可解密的内容的想法外，您还必须深入研究CCKeyDerivationPBKDF()（CommonKeyDerivation.h）的工作方式。
编辑：当您要求提供一种打包和解压缩盐， iv 和密码的方法时使用NSData非常简单。
+ (NSData *)packWithSalt:(NSData*)salt IV:(NSData*)iv Cypher:(NSData*)tocypher {
//adding Salt + IV + Cipher text
NSMutableData *combi = [NSMutableData data];
//[combi appendBytes:salt.bytes length:16];
//[combi appendBytes:iv.bytes length:16]; //16
//[combi appendBytes:tocypher.bytes length:tocypher.length];
[combi appendData:salt];
[combi appendData:iv];
[combi appendData:tocypher];
return combi;
}
+ (NSData*)cypherUnpackToSalt:(NSMutableData**)salt andIV:(NSMutableData**)iv fromPackData:(NSData*)pack {
void *sBuff[16] = {};
void *iBuff[16] = {};
NSUInteger len = pack.length - 16 - 16; //keep length flexible
void *pBuff = malloc(sizeof(Byte)*len); //needs dynamically size of buff
[pack getBytes:sBuff range:NSMakeRange(0,16)];
[pack getBytes:iBuff range:NSMakeRange(16,32)];
[pack getBytes:pBuff range:NSMakeRange(32,len)];
[(*salt) replaceBytesInRange:NSMakeRange(0,16) withBytes:sBuff];
[(*iv) replaceBytesInRange:NSMakeRange(0,16) withBytes:iBuff];
NSMutableData *unpack = [NSMutableData dataWithLength:len];
[unpack replaceBytesInRange:NSMakeRange(0,len) withBytes:pBuff];
free(pBuff);
return unpack;
}
将这两种方法的加密和解密集成起来应该非常简单。
概念证明：我们可以将所有内容打包在一起吗？并再次打开包装？
NSData *salt = [CryptAES randomDataOfLength:16];
NSData *iv = [CryptAES randomDataOfLength:16];
NSData *chunk = [CryptAES packWithSalt:salt IV:iv Cypher:plaintextData];
NSLog(@"salt=%@ iv=%@ pack=%@ ",[salt base64EncodedStringWithOptions:0],[iv base64EncodedStringWithOptions:0],[chunk base64EncodedStringWithOptions:0] );
NSMutableData *unSalt = [NSMutableData dataWithLength:16];
NSMutableData *unIv = [NSMutableData dataWithLength:16];
NSData *unchunk = [CryptAES cypherUnpackToSalt:&unSalt andIV:&unIv fromPackData:chunk];
NSString *plainAgain = [[NSString alloc] initWithData:unchunk encoding:NSUTF8StringEncoding];
NSLog(@"salt=%@ iv=%@ unpack=%@",[unSalt base64EncodedStringWithOptions:0],[unIv base64EncodedStringWithOptions:0],plainAgain );
因此，您的解密方法仍将需要密码参数。 这不是完美的方法，但是您绝不应该将加密数据及其密码一起扔掉（应该没问题），您只需要在用户端处理密码即可。我的意思是，否则整个加密都是没用的！
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