How to create RSA in Java?

What is the function of RSA in Java?

I was going through the RSA class in java.

I was a bit confused about what exactly it is for. RSA is for encryption and decryption? How does it differ from AES?
I read some articles on internet and none of them gave answer to my question. Can anyone explain how it is used in Java? RSA is a cryptography protocol. It has two core concepts: key generation, and encryption. You can generate keys, and encrypt information using those keys.

Key Generation. Key generation is just like any other cryptographic algorithm: you have a secure random number generator, and then you use that to pick values for your keys. In this case, it's a symmetric-key algorithm (the part that changes is randomized).

The reason you use symmetric algorithms for encryption, rather than just using a secure random number generator, is that it allows you to share a key between different instances of the encryption/decryption algorithm, and have them interoperate. You will need to read the details of the different encryption modes if you want to get a firm understanding of how to use them.

How to use RSA algorithm in Java?

The general algorithm is as follows.

Generate a public/private key pair using a random number generator. Encrypt the private key using the public key. Decrypt the ciphertext with the private key. For this example, you'd probably want to generate your keys using SecureRandom (or your favourite random number generator) and store them as a KeyPair. The private key would be stored in the KeyPair object.

KeyPair keyPair = new KeyPair(1, 2); // 1,2 are the keys. // 1. Generate a public/private key pair KeyFactory keyFactory = KeyFactory.getInstance("RSA"); KeySpec keySpec = keyFactory.getKeySpec(keyPair.getPublic(), KeyType.RSA);
PublicKey publicKey = keyFactory.generatePublic(keySpec); PrivateKey privateKey = keyFactory.generatePrivate(keySpec); // 2. Encrypt the private key with the public key Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.doFinal(privateKey.getEncoded());
// 3. Decrypt the ciphertext cipher.init(Cipher.doFinal(encrypted);
Here's an example using BouncyCastle. KeyPair keyPair = new KeyPair(1, 2); // 1,2 are the keys. // 1.getInstance("RSA", "BC"); KeySpec keySpec = keyFactory.getKeySpec(keyPair.getPublic(), KeyType.RSA);
PublicKey publicKey = keyFactory.generatePublic(keySpec); PrivateKey privateKey = keyFactory.generatePrivate(keySpec); // 2.getInstance("RSA"); cipher.init(Cipher.doFinal(privateKey.