Java Sample code for store cryptography key in a file

How to Store Crytography Key in a File in Java ?

Condition for Store Crytography Key in a File in Java

Description:
A common approach is to store the key in a binary format, ensuring that it is properly encoded and decoded when needed. If the key is symmetric, such as an AES key, it can be stored directly as a byte array. For asymmetric keys, such as RSA, the private and public keys can be stored separately as RSAPrivateKey and RSAPublicKey objects, serialized into files. Using a KeyStore is also an option for securely storing keys, as it provides additional protection against unauthorized access. When storing keys, ensuring that the file is properly secured, either by encryption or by using proper file access permissions, is critical to maintaining the confidentiality of the key.

AES Symmetric Key cryptography: AES (Advanced Encryption Standard) is a symmetric key encryption algorithm that uses the same key for both encryption and decryption. It operates on 128-bit blocks of data and supports key sizes of 128, 192, or 256 bits. AES performs multiple transformation rounds to securely encrypt plaintext into ciphertext. Its efficiency and strong security make it a widely used standard for encrypting data in various applications.

RSA Asymmetric Key cryptography: RSA (Rivest-Shamir-Adleman) is an asymmetric key cryptographic algorithm that uses a pair of keys: a public key for encryption and a private key for decryption. In this system, the public key is shared openly, while the private key is kept secret. RSA relies on the mathematical difficulty of factoring large prime numbers to provide security. Data encrypted with the public key can only be decrypted using the corresponding private key, and vice versa. RSA is commonly used for secure data transmission, digital signatures, and key exchange, offering a high level of security due to the complexity of its underlying mathematical principles.

Sample Code

Symmetric key (AES) :
package JavaSamples;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
public class SymmetricKey {
public static void main(String[] args) throws Exception {
KeyGenerator keyGen = KeyGenerator.getInstance("AES");
keyGen.init(256);
SecretKey secretKey = keyGen.generateKey();
File keyFile = new File("secretKey.key");
saveKeyToFile(secretKey, keyFile);
System.out.println("Key stored successfully in: " + keyFile.getAbsolutePath());
}
public static void saveKeyToFile(SecretKey key, File file) throws IOException {
byte[] keyBytes = key.getEncoded();
try (FileOutputStream fos = new FileOutputStream(file)) {
fos.write(keyBytes);
}
}
}

AsymmetricKey (RSA) :
package JavaSamples;
import java.io.FileOutputStream;
import java.io.File;
import java.io.IOException;
import java.security.*;
public class AsymmetricKey {
public static void main(String[] args) throws Exception {
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(2048);
KeyPair keyPair = keyGen.generateKeyPair();
PrivateKey privateKey = keyPair.getPrivate();
PublicKey publicKey = keyPair.getPublic();
File privateKeyFile = new File("private.key");
File publicKeyFile = new File("public.key");
saveKeyToFile(privateKey, privateKeyFile);
saveKeyToFile(publicKey, publicKeyFile); System.out.println("Public Key and Private Key generate successfully!");
}
public static void saveKeyToFile(Key key, File file) throws IOException {
byte[] keyBytes = key.getEncoded();
try (FileOutputStream fos = new FileOutputStream(file)) {
fos.write(keyBytes);
}
}
}

ScreenShots

To generate the secret key for AES Symmetric Algorithm :
To generate the public key for RSA Asymmetric Algorithm :
To generate the private key for RSA Asymmetric Algorithm :

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How to Store Crytography Key in a File in Java ?

Condition for Store Crytography Key in a File in Java

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