The C# is on the client end while Java code is used in a service. Windows phone encrypts the data while Java decrypts the data using the same symmetric key.
Below is my C# method for encryption
public static string EncryptAesTest(string data, string password)
{
SymmetricKeyAlgorithmProvider SAP = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.AesEcbPkcs7);
CryptographicKey AES;
HashAlgorithmProvider HAP = HashAlgorithmProvider.OpenAlgorithm(HashAlgorithmNames.Sha512);
Windows.Security.Cryptography.Core.CryptographicHash Hash_AES = HAP.CreateHash();
string encrypted;
try
{
byte[] hash = new byte[16];
Hash_AES.Append(CryptographicBuffer.CreateFromByteArray(System.Convert.FromBase64String(password)));
byte[] temp;
CryptographicBuffer.CopyToByteArray(Hash_AES.GetValueAndReset(), out temp);
Array.Copy(temp, 0, hash, 0, 16);
Array.Copy(temp, 0, hash, 15, 16);
AES = SAP.CreateSymmetricKey(CryptographicBuffer.CreateFromByteArray(hash));
IBuffer Buffer = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(data));
encrypted = CryptographicBuffer.EncodeToBase64String(CryptographicEngine.Encrypt(AES, Buffer, null));
return encrypted;
}
catch
{
return "encryption error";
}
}
Below is my Java class for decryption
private SecretKeySpec secretKey;
public void setKey() {
skey = "mykey";
MessageDigest sha = null;
try {
key = skey.getBytes("UTF-8");
logger.debug("Key length ====> " + key.length);
sha = MessageDigest.getInstance("SHA-512");
key = sha.digest(key);
key = Arrays.copyOf(key, 16); // use only first 128 bit
secretKey = new SecretKeySpec(key, "AES");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
public String decrypt(String strToDecrypt) {
Cipher cipher = null;
try {
cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");
cipher.init(Cipher.DECRYPT_MODE, this.secretKey);
setDecryptedString(new String(cipher.doFinal(Base64
.decodeBase64(strToDecrypt))));
} catch (Exception e) {
System.out.println("Error while decrypting: " + e.toString());
}
return null;
}
The key generation is not complete. For some reason, your C# code uses sets the last byte of the key to the same value as the first byte with the following code:
Array.Copy(temp, 0, hash, 0, 16);
Array.Copy(temp, 0, hash, 15, 16);
(To my understanding, this could should throw some exception, because you can't copy 16 bytes into the 16 byte array hash if you begin at index 15.)
You could do the same (bad) thing in Java
public void setKey() {
skey = "mykey";
MessageDigest sha = null;
try {
key = skey.getBytes("UTF-8");
logger.debug("Key length ====> " + key.length);
sha = MessageDigest.getInstance("SHA-512");
key = sha.digest(key);
key = Arrays.copyOf(key, 16); // use only first 128 bit
key[15] = key[0]; // added
secretKey = new SecretKeySpec(key, "AES");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
Things to consider:
ECB mode does not provide semantic security and it should never be used. Use at the very least CBC mode with a random IV for each encryption under the same key.
Passwords should be hashed multiple times. A single hash makes it easy for an attacker to brute-force the password, because this is operation is fast. You should use Password-based Encryption with a strong key derivation function like PBKDF2 (more than 100,000 iterations), scrypt or bcrypt. Don't forget to use a random salt.
Authenticate your ciphertexts. You would want to detect (malicious) manipulations of your ciphertexts in transit. This can be done either with an authenticated mode like GCM or EAX, or with an encrypt-then-MAC scheme by running a MAC algorithm over your ciphertexts. A strong MAC is HMAC-SHA256.
Related
I used below code for encryption using AES/ECB/PKCS5Padding algorith, function:
public static void setKey(String myKey) {
MessageDigest sha = null;
try {
key = myKey.getBytes("UTF-8");
sha = MessageDigest.getInstance("SHA-1");
key = sha.digest(key);
key = Arrays.copyOf(key, 16);
secretKey = new SecretKeySpec(key, "AES");
} catch (NoSuchAlgorithmException e) {
// e.printStackTrace();
} catch (UnsupportedEncodingException e) {
// e.printStackTrace();
}
}
public static String encrypt(String strToEncrypt, String secret) {
try {
setKey(secret);
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
return Base64.encodeToString(cipher.doFinal(strToEncrypt.getBytes("UTF-8")), Base64.DEFAULT);
} catch (Exception e) {
// System.out.println("Error while encrypting: " + e.toString());
}
return null;
}
Output:
Meeting ID : 20201228165764
Passcode: 769762
Encrypted values:
meetingid: LfD3obeP45AAGXYxPiByvQ==
passcode: fcJSdMArO3vUOL/WxwzRfw==
I used below AESEncryption code in iOS, but get a different encryption key, function:
func AESEncryption(key: String) -> String? {
let keyData: NSData! = (key as NSString).data(using: String.Encoding.utf8.rawValue) as NSData!
let data: NSData! = (self as NSString).data(using: String.Encoding.utf8.rawValue) as NSData!
let cryptData = NSMutableData(length: Int(data.length) + kCCBlockSizeAES128)!
let keyLength = size_t(kCCKeySizeAES128)
let operation: CCOperation = UInt32(kCCEncrypt)
let algoritm: CCAlgorithm = UInt32(kCCAlgorithmAES128)
let options: CCOptions = UInt32(kCCOptionECBMode + kCCOptionPKCS5Padding)
var numBytesEncrypted :size_t = 0
let cryptStatus = CCCrypt(operation,
algoritm,
options,
keyData.bytes, keyLength,
nil,
data.bytes, data.length,
cryptData.mutableBytes, cryptData.length,
&numBytesEncrypted)
if UInt32(cryptStatus) == UInt32(kCCSuccess) {
cryptData.length = Int(numBytesEncrypted)
var bytes = [UInt8](repeating: 0, count: cryptData.length)
cryptData.getBytes(&bytes, length: cryptData.length)
var hexString = ""
for byte in bytes {
hexString += String(format:"%02x", UInt8(byte))
}
return hexString}
return nil //Check condition nil
}
In android code secret key is generated is different than iOS. Can you please help to get same encrypted key from AES/ECB/PKS5padding algorithm? I am checking with https://8gwifi.org/CipherFunctions.jsp link.
In your Swift code, you're just using the string bytes as-is without hashing.
Note that you shouldn't be using SHA-1 for this; you should be using a KDF instead, or (most ideally) a prepackaged library that does all of this error-prone operation for you.
I have the following code on Java that decrypts AES encryption and I need to do the same on Node.js
private static SecretKeySpec secretKey;
private static byte[] key;
public static void setKey(String myKey) {
MessageDigest sha = null;
try {
key = myKey.getBytes("UTF-8");
sha = MessageDigest.getInstance("SHA-1");
key = sha.digest(key);
key = Arrays.copyOf(key, 16);
secretKey = new SecretKeySpec(key, "AES");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
public static String decrypt(String strToDecrypt, String secret)
{
try
{
setKey(secret);
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");
cipher.init(Cipher.DECRYPT_MODE, secretKey);
return new String(cipher.doFinal(Base64.getDecoder().decode(strToDecrypt)));
}
catch (Exception e)
{
System.out.println("Error while decrypting: " + e.toString());
}
return null;
}
I have tried using Crypt under the following code, but it doesn't give me the same results
var aesDecrypt = (text, password, bit) => {
var decipher = crypto.createDecipheriv('aes-' + bit + '-ecb', password, Buffer.alloc(0));
decipher.setAutoPadding(false);
return Buffer.concat([
decipher.update(text, 'base64'),
decipher.final()
]).toString();
};
How could I mimick that Java code from above into Node.js?
As James says, the Java code is hashing (and truncating) the password to form the key. Also it does use standard padding. The following works for ASCII data:
const crypto = require ('crypto');
const mydecrypt = (pw,ctx) => {
var h = crypto.createHash('sha1'); h.update(pw,'utf8'); var k = h.digest().slice(0,16);
var d = crypto.createDecipheriv('aes-128-ecb', k, Buffer.alloc(0));
return Buffer.concat([d.update(ctx,'base64'), d.final()]) .toString();
}
console.log(mydecrypt('password','ks7qtmk7kt5riV/Qyy3glQ=='));
->
testdata
It may not work for non-ASCII data. Java new String(byte[]) uses a JVM-dependent encoding which may be UTF8 or may be something different depending on your platform, build, and environment, none of which you described. OTOH nodejs Buffer.toString() always uses UTF8. You may need to change it to toString(somethingelse) to match the Java.
If this 'password' is truly a password, i.e. chosen or even remembered by one or more human(s), using a simple hash of it is very weak and will probably be broken if used for anything not utterly trivial; you should use a Password-Based Key Derivation Function designed for the purpose by someone competent, like older (PKCS5) PBKDF2 or newer bcrypt, scrypt, or argon2. However, that's not a programming question and is offtopic here; it has been discussed many times and at length on https://crypto.stackexchange.com and https://security.stackexchange.com .
I am currently making an Android app that includes encrypting a String with AES. But for some reason my app does not decrypt properly. I tried to change the Base64 format but it does not fix it. The code is similar to the example on Android Encryption with the Android Cryptography API
Does anyone know where did I go wrong with my functions? Since it does not decode to the same string as my encoded string ("pls").
Your help is much appreciated.
byte[] a = encryptFIN128AES("pls");
String b = decryptFIN128AES(a);
Log.e("AES_Test", "b = " + b);
/**
* Encrypts a string with AES (128 bit key)
* #param fin
* #return the AES encrypted byte[]
*/
private byte[] encryptFIN128AES(String fin) {
SecretKeySpec sks = null;
try {
sks = new SecretKeySpec(generateKey("Test1".toCharArray(), "Test2".getBytes()).getEncoded(),"AES");
} catch (Exception e) {
Log.e("encryptFIN128AES", "AES key generation error");
}
// Encode the original data with AES
byte[] encodedBytes = null;
try {
Cipher c = Cipher.getInstance("AES");
c.init(Cipher.ENCRYPT_MODE, sks);
encodedBytes = c.doFinal(fin.getBytes());
} catch (Exception e) {
Log.e("encryptFIN128AES", "AES encryption error");
}
return encodedBytes;
}
/**
* Decrypts a string with AES (128 bit key)
* #param encodedBytes
* #return the decrypted String
*/
private String decryptFIN128AES(byte[] encodedBytes) {
SecretKeySpec sks = null;
try {
sks = new SecretKeySpec(generateKey("Test1".toCharArray(), "Test2".getBytes()).getEncoded(),"AES");
} catch (Exception e) {
Log.e("decryptFIN128AES", "AES key generation error");
}
// Decode the encoded data with AES
byte[] decodedBytes = null;
try {
Cipher c = Cipher.getInstance("AES");
c.init(Cipher.DECRYPT_MODE, sks);
decodedBytes = c.doFinal(encodedBytes);
} catch (Exception e) {
Log.e("decryptFIN128AES", "AES decryption error");
}
return Base64.encodeToString(decodedBytes, Base64.DEFAULT);
}
public static SecretKey generateKey(char[] passphraseOrPin, byte[] salt)
throws NoSuchAlgorithmException, InvalidKeySpecException {
final int iterations = 1000;
// Generate a 256-bit key
final int outputKeyLength = 128;
SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
KeySpec keySpec = new PBEKeySpec(passphraseOrPin, salt, iterations, outputKeyLength);
SecretKey secretKey = secretKeyFactory.generateSecret(keySpec);
return secretKey;
}
Output:
E/AES_Test: b = cGxz
**
[EDIT] Modified my code but now there is a NullPointerException
**
/**
* Encrypts a string with AES (128 bit key)
* #param fin
* #return the AES encrypted string
*/
private byte[] encryptFIN128AES(String fin) {
SecretKeySpec sks = null;
try {
sks = new SecretKeySpec(generateKey(PASSPHRASE, SALT.getBytes(StandardCharsets.UTF_8)).getEncoded(), "AES");
} catch (Exception e) {
Log.e("encryptFIN128AES", "AES key generation error");
}
// Encode the original data with AES
byte[] encodedBytes = null;
try {
Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
c.init(Cipher.ENCRYPT_MODE, sks);
encodedBytes = c.doFinal(fin.getBytes(StandardCharsets.UTF_8));
} catch (Exception e) {
Log.e("encryptFIN128AES", "AES encryption error");
}
return encodedBytes;
}
/**
* Decrypts a string with AES (128 bit key)
* #param encodedBytes
* #return the decrypted String
*/
private String decryptFIN128AES(byte[] encodedBytes) {
SecretKeySpec sks = null;
try {
sks = new SecretKeySpec(generateKey(PASSPHRASE, SALT.getBytes(StandardCharsets.UTF_8)).getEncoded(), "AES");
} catch (Exception e) {
Log.e("decryptFIN128AES", "AES key generation error");
}
// Decode the encoded data with AES
byte[] decodedBytes = null;
try {
Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
c.init(Cipher.DECRYPT_MODE, sks);
decodedBytes = c.doFinal(encodedBytes);
} catch (Exception e) {
Log.e("decryptFIN128AES", "AES decryption error");
}
//return Base64.encodeToString(decodedBytes, Base64.DEFAULT);
return new String(decodedBytes, StandardCharsets.UTF_8);
}
// generateKey(char[] passphraseOrPin, byte[] salt) remains the same
Error:
E/decryptFIN128AES: AES decryption error
E/AndroidRuntime: FATAL EXCEPTION: Thread-176
Process: testapp.ttyi.nfcapp, PID: 2920
java.lang.NullPointerException: Attempt to get length of null array
at java.lang.String.<init>(String.java:371)
at testapp.ttyi.nfcapp.DisplayQRActivity.decryptFIN128AES(DisplayQRActivity.java:254)
at testapp.ttyi.nfcapp.DisplayQRActivity.access$100(DisplayQRActivity.java:29)
at testapp.ttyi.nfcapp.DisplayQRActivity$1.run(DisplayQRActivity.java:77)
at java.lang.Thread.run(Thread.java:818)
**
[EDIT2] Resolved (But no Padding/Encryption Mode allowed)
**
I managed to resolve the issue. (Decodes to "pls") using Codo's solution ofreturn new String(decodedBytes, StandardCharsets.UTF_8);
Though it only works when the algorithm used is:
Cipher c = Cipher.getInstance("AES");
When I put Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
The "NullPointerException" as seen above will happen. My observation shows that during decryption:
try {
Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
c.init(Cipher.DECRYPT_MODE, sks);
decodedBytes = c.doFinal(encodedBytes);
} catch (Exception e) {
Log.e("decryptFIN128AES", "AES decryption error");
}
something will fail and it will always print out:
E/decryptFIN128AES: AES decryption error
And thus the NullPointerException will occur as decodedBytes is always initiated to NULL.
Your process is not balanced. For encryption you do:
Encode string using default charset (fin.getBytes()) to get binary data
Encrypt binary data to get encrypted data (doFinal)
For the decryption, you do:
Decrypt encrypted data to get unencrypted binary data (doFinal)
Encode binary data as a Base64 string
Instead of Base64 encoding, the last step should be the reverse of step 1 in the encryption, i.e. you should decode the binary data into a string:
return String(decodedBytes);
It strongly recommend, you do not use the default charset for encoding and decoding as it depends on the system's setting. So it could be different between the system where you encrypt and decyrpt.
So use:
fin.getBytes(StandardCharsets.UTF_8);
and:
return String(decodedBytes, StandardCharsets.UTF_8);
The same applies for the salt.
Also note that you should specify the padding and chaining mode. If you don't, provider-specific default values apply. See #Ryan's answer for more details.
You should research more on how to use AES correctly as you are missing some basic fundamentals of AES security: no IV (assuming using CBC), no mode specified (such as CBC), and no padding specified (such as PKCS5).
Looks like char encoding issue. With minor modifications it works.
in encryptFIN128AES:
encodedBytes = c.doFinal(Base64.getEncoder().encode(fin.getBytes()));
in decryptFIN128AES:
return new String(Base64.getDecoder().decode(decodedBytes));
I have recently used the AES CBC 128 algorithm in Java in order to cipher data. Now I need to rebuild that algorithm in PHP, but I have no idea how, because PHP algorithms on the internet return different results. Maybe you can help me.
This is the Java-code to encrypt:
private SecretKeySpec secretKey;
private IvParameterSpec ivSpec;
public void setKey(String myKey) {
MessageDigest sha = null;
try {
byte[] key = myKey.getBytes("UTF-8");
sha = MessageDigest.getInstance("SHA-1");
key = sha.digest(key);
key = Arrays.copyOf(key, 16);
secretKey = new SecretKeySpec(key, "AES");
byte[] iv = new String("1010101010101010").getBytes("UTF-8");
ivSpec = new IvParameterSpec(iv);
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
public String encrypt(String strToEncrypt) {
try {
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);
return Base64.encode(cipher.doFinal(strToEncrypt.getBytes("UTF-8")));
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public String decrypt(String strToDecrypt) {
try {
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);
return new String(cipher.doFinal(Base64.decode(strToDecrypt)));
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public static void main(String[] args) {
AESText aes = new AESText();
final String secretKey = "com.secure.test.projectjasdS/FjkGkGhkGjhG786Vjfg=tjGFGH";
aes.setKey(secretKey);
String originalString = "test set se ts et set s et se";
String encryptedString = aes.encrypt(originalString);
String decryptedString = aes.decrypt(encryptedString);
System.out.println("origin: " + originalString);
System.out.println("encrypted: " + encryptedString);
System.out.println("decrypted: " + decryptedString);
}
This is my php code:
protected $key;
protected $method = 'AES-128-CBC';
protected $iv = '1010101010101010';
protected $option = OPENSSL_CIPHER_AES_128_CBC;
function __construct($key)
{
$this->key = $key;
}
public function encrypt($data) {
if (is_null($data)) {
return "Error " . INVALID_PARAMS_ENCRYPTIONS . ": Data is null ";
}
$enc = openssl_encrypt($data, $this->method, $this->key, $this->option, $this->iv);
return base64_encode($enc);
}
public function decrypt($data) {
if (is_null($data)) {
return "Error " . INVALID_PARAMS_ENCRYPTIONS . ": Data is null ";
}
$data = base64_decode($data);
$dec = openssl_decrypt($data, $this->method, $this->key, $this->option, $this->iv);
return $dec;
}
When I encrypted data from java encryption, This result cannot decrypt on Php decryption.
Can you guys possibly help me with building a PHP script, that returns the same results with java encryption?
At first glance I see three issues here:
First: you are not using the same mode: in java you have AES/ECB/PKCS5Padding whereas your php uses AES-128-CBC.
Second: you probably aren't using the same IV's in the Java and PHP code (IV's are irrelevant for ECB, but once you switch your java to CBC you will need it):
You have $iv = '1010101010101010' (which is then passed to openssl) in your php but nothing like that in your java.
At the very least, you will probably need something like that in your Java part as well:
cipher.init(Cipher.DECRYPT_MODE/ENCRYPT_MODE, secretKey, new IvParameterSpec(iv))
with iv being a byte[] containing your IV bytes.
Third: once the problems above are addressed, padding may be the next breaking thing: your java cipher specification mentions PKCS5Padding. You need to make sure that both of your counterparts use the same.
edit: Fourth: One more issue is the way you derive the key bits to be used. In java you take the first 16 bytes of a sha1-hash, and in php you just pass $key to openssl. openssl might be deriving the encryption key in a different way.
When building cryptography-related tools using block ciphers, it's always nice to revisit classics like Block cipher mode of operation and Padding on Wikipedia, to get a sense of what is going on under the hood.
Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 8 years ago.
Improve this question
In my project I have provided "Encryption and Decryption" through Multi Level algorithms.
I used RSA and 3DES for this. Now I want to calculate its time complexity for performance analysis. I am a little bit confused here. How to exactly calculate it or what's the time complexity for it.
Following is the Algo.
Helper Class
class Helper{
public Cipher dcipher,ecipher;
public Helper(String passPhrase){
byte[] salt =
{ (byte)0xA9, (byte)0x9B, (byte)0xC8, (byte)0x32,
(byte)0x56, (byte)0x34, (byte)0xE3, (byte)0x03
};
int iterationCount = 19;
try {
KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt,
iterationCount);
SecretKey key =
SecretKeyFactory.getInstance("PBEWithMD5AndDES").generateSecret(keySpec);
ecipher = Cipher.getInstance(key.getAlgorithm());
dcipher = Cipher.getInstance(key.getAlgorithm());
AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt,
iterationCount);
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
}
catch(Exception e){ }
}
#SuppressWarnings("unused")
protected String encrypt(String str){
try{
byte[] utf8 = str.getBytes("UTF8");
byte[] enc = ecipher.doFinal(utf8);
return new sun.misc.BASE64Encoder().encode(enc);
}
catch (Exception e) { }
return null;
}
// Decrpt password
//To decrypt the encryted password
protected String decrypt(String str) {
Cipher dcipher = null;
try{
byte[] salt = {(byte)0xA9, (byte)0x9B, (byte)0xC8, (byte)0x32,(byte)0x56,
(byte)0x34, (byte)0xE3, (byte)0x03};
int iterationCount = 19;
try{
String passPhrase="";
KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt,
iterationCount);
SecretKey key =
SecretKeyFactory.getInstance("PBEWithMD5AndDES").generateSecret(keySpec);
dcipher = Cipher.getInstance(key.getAlgorithm());
// Prepare the parameters to the cipthers
AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt,
iterationCount);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
}
catch (Exception e) {
System.out.println("EXCEPTION: InvalidAlgorithmParameterException");
}
byte[] dec = new sun.misc.BASE64Decoder().decodeBuffer(str);
// Decrypt
byte[] utf8 = dcipher.doFinal(dec);
// Decode using utf-8
return new String(utf8, "UTF8");
}
catch (BadPaddingException e) {
} catch (IllegalBlockSizeException e) {
} catch (UnsupportedEncodingException e) {
} catch (IOException e){
}
return null;
}
MultilevelEnc Class
public String Encrypt()
{
try
{
KeyPairGenerator kpg=KeyPairGenerator.getInstance("RSA");
kpg.initialize(512);//initialize key pairs to 512 bits ,you can also take 1024 or 2048 bits
kp=kpg.genKeyPair();
PublicKey publi=kp.getPublic();
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, publi);
byte[]src=srci.getBytes();//converting source data into byte array
cipherData = cipher.doFinal(src);//use this method to finally encrypt data
srco=new String(cipherData);//converting byte array into string
}
catch(Exception e)
{
}
return srco;
}
public String Decrypt(String cipherdata)
{
try
{
PrivateKey privatei=kp.getPrivate();//Generating private key
Cipher cipheri=Cipher.getInstance("RSA");//Intializing 2nd instance of Cipher class
cipheri.init(Cipher.DECRYPT_MODE, privatei);//Setting to decrypt_mode
byte[] cipherDat = cipheri.doFinal(cipherData);//Finally decrypting data
decryptdata=new String(cipherDat);
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
return decryptdata;
}
Main Class
public static void main(String args[])
{
String odata = "abcd";
String encdata2;
String decrypt2;
String decrypt1;
MultilevelEnc r = new MultilevelEnc(odata);
String encdata = r.Encrypt(); // RSA Algo Encryption
Helper h = new Helper("");
encdata2 = h.encrypt(encdata); // 3Des Algo Encryption
decrypt2 = h.decrypt(encdata2); // 3Des Decryption
decrypt1 = r.Decrypt(decrypt2); // RSA Decryption
}
To the best of my knowledge, all standard encryption algorithms these days work by applying a block cipher to different pieces of the input, one after the other, after doing some quick preprocessing on each block. Each block cipher works on a fixed-size input and thus has runtime O(1) (though it may be a large O(1)), so the runtime of each of the encryption and decryption algorithms should be O(n) (O(n) blocks to process, O(1) time per block). You're running a fixed number of iterations of this cipher, so the runtime should be O(n) as well.
To get a rough estimate of the wall-clock runtime, you can use the System.nanoTime function to get an estimate of the current time in nanoseconds, then perform your operations, and call System.nanoTime again to get the current time again. The difference then gives you the total runtime.
Hope this helps!