Public-Key Encryption: Fundamentals and Applications

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import javax.crypto.Cipher;

public class PublicKeyEncryptionExample {
    public static void main(String[] args) throws Exception {
        // Gerar par de chaves
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(2048);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        // Criptografar dados
        Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPPadding");
        cipher.init(Cipher.ENCRYPT_MODE, keyPair.getPublic());
        byte[] encryptedData = cipher.doFinal("Dados secretos".getBytes());

        // Descriptografar dados
        cipher.init(Cipher.DECRYPT_MODE, keyPair.getPrivate());
        byte[] decryptedData = cipher.doFinal(encryptedData);

        System.out.println(new String(decryptedData));
    }
}

from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import padding

# Gerar par de chaves RSA
private_key = rsa.generate_private_key(
    public_exponent=65537,
    key_size=2048
)

# Obter a chave pública
public_key = private_key.public_key()

# Criptografar dados
encrypted = public_key.encrypt(
    b"Dados secretos",
    padding.OAEP(
        mgf=padding.MGF1(algorithm=hashes.SHA256()),
        algorithm=hashes.SHA256(),
        label=None
    )
)

# Descriptografar dados
decrypted = private_key.decrypt(
    encrypted,
    padding.OAEP(
        mgf=padding.MGF1(algorithm=hashes.SHA256()),
        algorithm=hashes.SHA256(),
        label=None
    )
)

print(decrypted)