import java.nio.charset.StandardCharsets;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.util.Arrays;
import java.util.Base64;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
/**
*
* OpenSSL equivalent for AES encryption with and without PBKDF2 and key-obtention iteration (-iter)
*
* References:
*
*
*/
public class AesStringEncryptor {
private static final byte[] SALTED_MAGIC = "Salted__".getBytes();
private final String pbeAlgorithm;
private final String digestAlgorithm;
private final int keyLengthInByte;
private String encryptionPassword = "";
private int keyObtentionIterations = 10000; // 10000 is openssl's default
/**
*
* @param pbeAlgorithm - "AES/CBC/PKCS5Padding", "AES/ECB/PKCS5Padding"
* @param digestAlgorithm - "SHA-256", "MD5"
* @param keyLengthInBit - 128, 256
* @throws NoSuchPaddingException
* @throws NoSuchAlgorithmException
*/
public AesStringEncryptor(String pbeAlgorithm, String digestAlgorithm, int keyLengthInBit) throws NoSuchAlgorithmException, NoSuchPaddingException {
super();
this.pbeAlgorithm = pbeAlgorithm;
this.digestAlgorithm = digestAlgorithm;
this.keyLengthInByte = keyLengthInBit / 8;
}
public String getEncryptionPassowrd() {
return encryptionPassword;
}
public void setEncryptionPassowrd(String encryptionPassowrd) {
this.encryptionPassword = encryptionPassowrd;
}
public int getKeyObtentionIterations() {
return keyObtentionIterations;
}
public void setKeyObtentionIterations(int keyObtentionIterations) {
this.keyObtentionIterations = keyObtentionIterations;
}
public String encryptString(String clearText, String password)
throws InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException {
return this.encryptString(clearText, password, false, -1);
}
public String encryptString(String clearText)
throws InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException {
return this.encryptString(clearText, this.encryptionPassword);
}
public String encryptStringWithPBKDF2(String clearText, String password, int hashIterations)
throws InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException {
return this.encryptString(clearText, password, true, hashIterations);
}
private String encryptString(String clearText, String password, boolean pbkdf2, int hashIterations)
throws InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException {
final byte[] salt = (new SecureRandom()).generateSeed(8);
final byte[] inBytes = clearText.getBytes(StandardCharsets.UTF_8);
byte[] keyAndIv = new byte[0];
if(pbkdf2) {
keyAndIv = deriveKeyAndIvWithPBKDF2(password, hashIterations, salt);
}else {
keyAndIv = deriveKeyAndIv(password.getBytes(StandardCharsets.ISO_8859_1), salt);
}
// AES-256: 32 bytes key, 16 bytes iv
// AES-128: 16 bytes key, 16 bytes iv
final byte[] keyValue = Arrays.copyOfRange(keyAndIv, 0, this.keyLengthInByte);
final SecretKeySpec key = new SecretKeySpec(keyValue, "AES");
Cipher cipher = Cipher.getInstance(this.pbeAlgorithm);
if(this.pbeAlgorithm.contains("ECB")) {
cipher.init(Cipher.ENCRYPT_MODE, key);
}else {
// CBC
final byte[] iv = Arrays.copyOfRange(keyAndIv, this.keyLengthInByte, (this.keyLengthInByte + 16));
cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(iv));
}
byte[] data = cipher.doFinal(inBytes);
data = array_concat(array_concat(SALTED_MAGIC, salt), data);
return Base64.getEncoder().encodeToString( data );
}
public String encryptStringWithPBKDF2(String clearText)
throws InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException {
return this.encryptStringWithPBKDF2(clearText, encryptionPassword, keyObtentionIterations);
}
public String encryptStringWithPBKDF2(String clearText, String password)
throws InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException {
return this.encryptStringWithPBKDF2(clearText, password, keyObtentionIterations);
}
public String decrypt(String encryptedBase64, String password)
throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException {
return this.decrypt(encryptedBase64, password, false, -1);
}
public String decrypt(String encryptedBase64)
throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException {
return this.decrypt(encryptedBase64, this.encryptionPassword);
}
public String decryptWithPBKDF2(String encryptedBase64, String password, int hashIterations)
throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException {
return this.decrypt(encryptedBase64, password, true, hashIterations);
}
private String decrypt(String encryptedBase64, String password, boolean pbkdf2, int hashIterations)
throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException {
final byte[] inBytes = Base64.getDecoder().decode(encryptedBase64);
final byte[] shouldBeMagic = Arrays.copyOfRange(inBytes, 0, SALTED_MAGIC.length);
if (!Arrays.equals(shouldBeMagic, SALTED_MAGIC)) {
throw new IllegalArgumentException("Bad magic number. Initial bytes from input do not match OpenSSL SALTED_MAGIC salt value.");
}
final byte[] salt = Arrays.copyOfRange(inBytes, SALTED_MAGIC.length, SALTED_MAGIC.length + 8);
byte[] keyAndIv = new byte[0];
if(pbkdf2) {
keyAndIv = deriveKeyAndIvWithPBKDF2(password, hashIterations, salt);
}else {
keyAndIv = deriveKeyAndIv(password.getBytes(StandardCharsets.ISO_8859_1), salt);
}
final byte[] keyValue = Arrays.copyOfRange(keyAndIv, 0, this.keyLengthInByte);
final SecretKeySpec key = new SecretKeySpec(keyValue, "AES");
Cipher cipher = Cipher.getInstance(this.pbeAlgorithm);
if(this.pbeAlgorithm.contains("ECB")) {
cipher.init(Cipher.DECRYPT_MODE, key);
}else {
// CBC
final byte[] iv = Arrays.copyOfRange(keyAndIv, this.keyLengthInByte, (this.keyLengthInByte + 16));
cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
}
final byte[] clear = cipher.doFinal(inBytes, 16, inBytes.length - 16);
return new String(clear, StandardCharsets.UTF_8);
}
public String decryptWithPBKDF2(String encryptedBase64)
throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException {
return this.decryptWithPBKDF2(encryptedBase64, this.encryptionPassword, this.keyObtentionIterations);
}
public String decryptWithPBKDF2(String encryptedBase64, String password)
throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException {
return this.decryptWithPBKDF2(encryptedBase64, password, this.keyObtentionIterations);
}
private byte[] deriveKeyAndIv(final byte[] pass, final byte[] salt) throws NoSuchAlgorithmException {
MessageDigest md = MessageDigest.getInstance(this.digestAlgorithm);
final byte[] passAndSalt = array_concat(pass, salt);
byte[] hash = new byte[0];
byte[] keyAndIv = new byte[0];
for (int i = 0; i < 3 && keyAndIv.length < 48; i++) {
final byte[] hashData = array_concat(hash, passAndSalt);
hash = md.digest(hashData);
keyAndIv = array_concat(keyAndIv, hash);
}
return keyAndIv;
}
private byte[] deriveKeyAndIvWithPBKDF2(String password, int hashIterations, final byte[] salt)
throws NoSuchAlgorithmException, InvalidKeySpecException {
SecretKeyFactory keyFactory = null;
if("SHA-256".equals(this.digestAlgorithm)) {
keyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
} else {
// MD5
// "In addition, MD5 hash function is forbidden to be used with PBKDF2 such as PBKDF2WithHmacMD5."
throw new UnsupportedOperationException("MD5 hash function is not supported with PBKDF2");
}
PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray(), salt, hashIterations, 48 * 8);
byte[] keyAndIv = keyFactory.generateSecret(keySpec).getEncoded();
return keyAndIv;
}
private byte[] array_concat(final byte[] a, final byte[] b) {
final byte[] c = new byte[a.length + b.length];
System.arraycopy(a, 0, c, 0, a.length);
System.arraycopy(b, 0, c, a.length, b.length);
return c;
}
public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, InvalidKeySpecException {
String encrypted = "";
// echo -n plainTextToEncrypt| openssl enc -base64 -aes-256-cbc -md sha256 -pass pass:secretKey -p
AesStringEncryptor aes256Cbc = new AesStringEncryptor("AES/CBC/PKCS5Padding", "SHA-256", 256);
encrypted = aes256Cbc.encryptString("plainTextToEncrypt", "secretKey");
System.out.println("Encrypted aes-256-cbc sha256: " + encrypted + " , Decrypted: " + aes256Cbc.decrypt(encrypted, "secretKey"));
// echo -n plainTextToEncrypt| openssl enc -base64 -aes-256-cbc -md sha256 -pass pass:secretKey -p -pbkdf2
encrypted = aes256Cbc.encryptStringWithPBKDF2("plainTextToEncrypt", "secretKey");
System.out.println("Encrypted aes-256-cbc sha256 pbkdf2: " + encrypted + ", Decrypted: " + aes256Cbc.decryptWithPBKDF2(encrypted, "secretKey") );
AesStringEncryptor aes128Cbc = new AesStringEncryptor("AES/CBC/PKCS5Padding", "SHA-256", 128);
encrypted = aes128Cbc.encryptString("plainTextToEncrypt", "secretKey");
System.out.println("Encrypted aes-128-cbc sha256: " + encrypted + " , Decrypted: " + aes128Cbc.decrypt(encrypted, "secretKey"));
encrypted = aes128Cbc.encryptStringWithPBKDF2("plainTextToEncrypt", "secretKey");
System.out.println("Encrypted aes-128-cbc sha256 pbkdf2: " + encrypted + ", Decrypted: " + aes128Cbc.decryptWithPBKDF2(encrypted, "secretKey") );
AesStringEncryptor aes256Ecb = new AesStringEncryptor("AES/ECB/PKCS5Padding", "SHA-256", 256);
encrypted = aes256Ecb.encryptString("plainTextToEncrypt", "secretKey");
System.out.println("Encrypted aes-256-ecb sha256: " + encrypted + " , Decrypted: " + aes256Ecb.decrypt(encrypted, "secretKey"));
// echo -n plainTextToEncrypt| openssl enc -base64 -aes-256-cbc -md md5 -pass pass:secretKey -p
AesStringEncryptor aes256EcbMd5 = new AesStringEncryptor("AES/ECB/PKCS5Padding", "MD5", 256);
encrypted = aes256EcbMd5.encryptString("plainTextToEncrypt", "secretKey");
System.out.println("Encrypted aes-256-ecb md5: " + encrypted + " , Decrypted: " + aes256EcbMd5.decrypt(encrypted, "secretKey"));
// Not supported
// encrypted = aes256EcbMd5.encryptStringWithPBKDF2("plainTextToEncrypt", "secretKey");
// System.out.println("Encrypted aes-256-ecb md5 pbkdf2: " + encrypted + " , Decrypted: " + aes256EcbMd5.decryptWithPBKDF2(encrypted, "secretKey"));
}
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// add dependencies here as below
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Java is a very popular general-purpose programming language, it is class-based and object-oriented. Java was developed by James Gosling at Sun Microsystems ( later acquired by Oracle) the initial release of Java was in 1995. Java 17 is the latest long-term supported version (LTS). As of today, Java is the world's number one server programming language with a 12 million developer community, 5 million students studying worldwide and it's #1 choice for the cloud development.
short x = 999; // -32768 to 32767
int x = 99999; // -2147483648 to 2147483647
long x = 99999999999L; // -9223372036854775808 to 9223372036854775807
float x = 1.2;
double x = 99.99d;
byte x = 99; // -128 to 127
char x = 'A';
boolean x = true;
When ever you want to perform a set of operations based on a condition If-Else is used.
if(conditional-expression) {
// code
} else {
// code
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Example:
int i = 10;
if(i % 2 == 0) {
System.out.println("i is even number");
} else {
System.out.println("i is odd number");
}
Switch is an alternative to If-Else-If ladder and to select one among many blocks of code.
switch(<conditional-expression>) {
case value1:
// code
break; // optional
case value2:
// code
break; // optional
...
default:
//code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition. Usually for loop is preferred when number of iterations is known in advance.
for(Initialization; Condition; Increment/decrement){
//code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while(<condition>){
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (<condition>);
Class is the blueprint of an object, which is also referred as user-defined data type with variables and functions. Object is a basic unit in OOP, and is an instance of the class.
class keyword is required to create a class.
class Mobile {
public: // access specifier which specifies that accessibility of class members
string name; // string variable (attribute)
int price; // int variable (attribute)
};
Mobile m1 = new Mobile();
public class Greeting {
static void hello() {
System.out.println("Hello.. Happy learning!");
}
public static void main(String[] args) {
hello();
}
}
Collection is a group of objects which can be represented as a single unit. Collections are introduced to bring a unified common interface to all the objects.
Collection Framework was introduced since JDK 1.2 which is used to represent and manage Collections and it contains:
This framework also defines map interfaces and several classes in addition to Collections.
| Collection | Description |
|---|---|
| Set | Set is a collection of elements which can not contain duplicate values. Set is implemented in HashSets, LinkedHashSets, TreeSet etc |
| List | List is a ordered collection of elements which can have duplicates. Lists are classified into ArrayList, LinkedList, Vectors |
| Queue | FIFO approach, while instantiating Queue interface you can either choose LinkedList or PriorityQueue. |
| Deque | Deque(Double Ended Queue) is used to add or remove elements from both the ends of the Queue(both head and tail) |
| Map | Map contains key-values pairs which don't have any duplicates. Map is implemented in HashMap, TreeMap etc. |