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Java decrypt and verify

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This example demonstrates how to decrypt a file that has been OpenPGP signed and encrypted in one pass. We can still decrypt it with the standard decrypt method, but with decrypt and verify in one pass we can also verify that the sender of the message is the one that we expect.

In order to run the decrypt and verify method we need our private key (to decrypt the message) and the public key of the sender (to verify the digital signature).

Decrypt file with keys located in files on the disk
Decrypt file with keys located in a KeyStore

Decrypt stream with keys supplied also as streams
Decrypt stream with keys located in a KeyStore

Decrypt and verify file with keys located in files on the disk

Note that even if the signature is invalid the contained file will be extracted.

import com.didisoft.pgp.PGPLib;
 
public class DecryptAndVerify {
 public static void main(String[] args) throws Exception{
  // create an instance of the library
  PGPLib pgp = new PGPLib();
 
  boolean validSignature = 
	pgp.decryptAndVerifyFile("encrypted.pgp", 
				"my_private_key.asc", "private key pass", 
				"sender_public_key.asc", 
				"OUTPUT.txt");
  if (validSignature) {
	System.out.println("Signature is valid.");
  } else {
	System.out.println("!Signature is invalid!");
  }
 }
}

Decrypt file with keys located in a KeyStore

We must specify our password for the private key that will be used to decrypt the file (the library searches for a key with Key ID equal to the one used to encrypt the file). For the verification a public key with Key ID equal to the one in the digital signature is searched among the public keys stored in the KeyStore.

import com.didisoft.pgp.KeyStore;
import com.didisoft.pgp.PGPLib;
 
public class KeystoreDecryptAndVerifyFile {
 public static void main(String[] args) throws Exception{
  // create an instance of the KeyStore
  KeyStore keyStore = new KeyStore("pgp.keystore", "changeit");
 
  // initialize the library 
  PGPLib pgp = new PGPLib();
 
  // our private decryption key password
  String privateKeyPassword = "changeit";
 
  boolean validSignature = 
     pgp.decryptAndVerifyFile("encrypted.pgp", 
				keyStore, 
				privateKeyPassword, 
				"OUTPUT.txt");
 
  if (validSignature) {
	System.out.println("Signature is valid.");
  } else {
	System.out.println("Signature is invalid!");
  }
 }
}

Decrypt stream with keys supplied as streams

This method gives more freedom on how the encrypted data and OpenPGP keys  are stored.

import java.io.FileOutputStream;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.OutputStream;
 
import com.didisoft.pgp.PGPLib;
 
public class DecryptAndVerifyStream {
 public static void main(String[] args) throws Exception{
  // create an instance of the library
  PGPLib pgp = new PGPLib();
 
  // obtain a signed and encrypted data stream
  InputStream encryptedStream = new FileInputStream("encrypted.pgp");
 
  InputStream privateKeyStream = new FileInputStream("private.key");
  String privateKeyPassword = "changeit";
 
  InputStream senderPublicKeyStream = new FileInputStream("public.key");
 
  // specify the destination stream of the decrypted data
  OutputStream decryptedStream = new FileOutputStream("OUTPUT.txt");
 
  boolean validSignature = 
	pgp.decryptAndVerifyStream(encryptedStream, 
				privateKeyStream, privateKeyPassword, 
				senderPublicKeyStream, 
				decryptedStream);
  if (validSignature) {
	System.out.println("Signature is valid.");
  } else {
	System.out.println("Signature is invalid!");
  }
 }
}

Decrypt stream with keys located in a KeyStore

This example is equivalent to the decrypt above, only the encrypted data and the decrypted output are streams.

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
 
import com.didisoft.pgp.KeyStore;
import com.didisoft.pgp.PGPLib;
 
public class KeyStoreDecryptAndVerifyStream {
 public static void main(String[] args) throws Exception{
  // create an instance of the KeyStore
  KeyStore keyStore = new KeyStore("pgp.keystore", "changeit");
 
  // initialize the library 
  PGPLib pgp = new PGPLib();
 
  // our private decryption key password
  String privateKeyPassword = "changeit";
 
  // obtain an encrypted stream
  InputStream encryptedStream = new FileInputStream("encrypted.pgp");
  // specify the decrypted output stream
  OutputStream decryptedStream = new FileOutputStream("OUTPUT.txt");
 
  boolean validSignature = 
     pgp.decryptAndVerifyStream(encryptedStream, 
				keyStore, 
				privateKeyPassword, 
				decryptedStream);
 
  if (validSignature) {
	System.out.println("Signature is valid.");
  } else {
	System.out.println("Signature is invalid!");
  }
 }
}

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