openPGP加解密示例

openPGP ：郵件加密標準，被廣泛使用

準備作業：

bouncycastle 的jar包

<dependency>
　　<groupId>org.bouncycastle</groupId>
　　<artifactId>bcprov-jdk15on</artifactId>
　　<version>1.50</version>
</dependency>

<dependency>
　　<groupId>org.bouncycastle</groupId>
　　<artifactId>bcpg-jdk15on</artifactId>
　　<version>1.50</version>
</dependency>

https://www.oracle.com/java/technologies/

搜索下載 Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files

將壓縮包中的 jar包替換 %JAVA_HOME%/jre/lib/security 或者 %JRE_HOME%/lib/security  目錄中的jar包 （目的是為了防止程式出現 Invalid Key size的錯誤）

原始碼如下：（可以參考 bcpg-jdk15on jar包里面的 examples目錄）

Security.addProvider(new BouncyCastleProvider());這句是必須的，否則程式會報錯

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.NoSuchProviderException;
import java.security.SecureRandom;
import java.security.Security;
import java.util.Iterator;

import org.bouncycastle.bcpg.ArmoredOutputStream;
import org.bouncycastle.bcpg.CompressionAlgorithmTags;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openpgp.PGPCompressedData;
import org.bouncycastle.openpgp.PGPCompressedDataGenerator;
import org.bouncycastle.openpgp.PGPEncryptedData;
import org.bouncycastle.openpgp.PGPEncryptedDataGenerator;
import org.bouncycastle.openpgp.PGPEncryptedDataList;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPLiteralData;
import org.bouncycastle.openpgp.PGPObjectFactory;
import org.bouncycastle.openpgp.PGPOnePassSignatureList;
import org.bouncycastle.openpgp.PGPPrivateKey;
import org.bouncycastle.openpgp.PGPPublicKey;
import org.bouncycastle.openpgp.PGPPublicKeyEncryptedData;
import org.bouncycastle.openpgp.PGPPublicKeyRing;
import org.bouncycastle.openpgp.PGPPublicKeyRingCollection;
import org.bouncycastle.openpgp.PGPSecretKey;
import org.bouncycastle.openpgp.PGPSecretKeyRingCollection;
import org.bouncycastle.openpgp.PGPUtil;
import org.bouncycastle.openpgp.operator.jcajce.JcePBESecretKeyDecryptorBuilder;
import org.bouncycastle.openpgp.operator.jcajce.JcePGPDataEncryptorBuilder;
import org.bouncycastle.openpgp.operator.jcajce.JcePublicKeyDataDecryptorFactoryBuilder;
import org.bouncycastle.openpgp.operator.jcajce.JcePublicKeyKeyEncryptionMethodGenerator;
import org.bouncycastle.util.io.Streams;

public class OpenPgpUtil {
    static {
        try {
            Security.addProvider(new BouncyCastleProvider());
        } catch (Exception e) {
           e.printStackTrace();
        }
    }

    public static void encryptFile(String outputFileName, String inputFileName, String encKeyFileName, boolean armor,
            boolean withIntegrityCheck) throws IOException, NoSuchProviderException, PGPException {
        OutputStream out = null;
        try {
            out = new BufferedOutputStream(new FileOutputStream(outputFileName));
            PGPPublicKey encKey = readPublicKey(encKeyFileName);
            encryptFile(out, inputFileName, encKey, armor, withIntegrityCheck);
        } finally {
            if(out!=null) {
                out.close();
            }
        }
    }

    public static void encryptFile(OutputStream out, String fileName, PGPPublicKey encKey, boolean armor,
            boolean withIntegrityCheck) throws IOException, NoSuchProviderException, PGPException {
        if (armor) {
            out = new ArmoredOutputStream(out);
        }

        byte[] bytes = compressFile(fileName, CompressionAlgorithmTags.ZIP);

        PGPEncryptedDataGenerator encGen = new PGPEncryptedDataGenerator(
                new JcePGPDataEncryptorBuilder(PGPEncryptedData.CAST5).setWithIntegrityPacket(withIntegrityCheck)
                        .setSecureRandom(new SecureRandom()).setProvider("BC"));

        encGen.addMethod(new JcePublicKeyKeyEncryptionMethodGenerator(encKey).setProvider("BC"));

        OutputStream cOut = encGen.open(out, bytes.length);

        cOut.write(bytes);
        cOut.close();

        if (armor) {
            out.close();
        }
    }

    public static byte[] compressFile(String fileName, int algorithm) throws IOException {
        ByteArrayOutputStream bOut = new ByteArrayOutputStream();
        PGPCompressedDataGenerator comData = new PGPCompressedDataGenerator(algorithm);
        PGPUtil.writeFileToLiteralData(comData.open(bOut), PGPLiteralData.BINARY, new File(fileName));
        comData.close();
        return bOut.toByteArray();
    }

    public static PGPPublicKey readPublicKey(String fileName) throws IOException, PGPException {
        InputStream keyIn = new BufferedInputStream(new FileInputStream(fileName));
        PGPPublicKey pubKey = readPublicKey(keyIn);
        keyIn.close();
        return pubKey;
    }

    @SuppressWarnings("rawtypes")
    private static PGPPublicKey readPublicKey(InputStream input) throws IOException, PGPException {
        PGPPublicKeyRingCollection pgpPub = new PGPPublicKeyRingCollection(PGPUtil.getDecoderStream(input));

        //
        // we just loop through the collection till we find a key suitable for
        // encryption, in the real
        // world you would probably want to be a bit smarter about this.
        //

        Iterator keyRingIter = pgpPub.getKeyRings();
        while (keyRingIter.hasNext()) {
            PGPPublicKeyRing keyRing = (PGPPublicKeyRing) keyRingIter.next();

            Iterator keyIter = keyRing.getPublicKeys();
            while (keyIter.hasNext()) {
                PGPPublicKey key = (PGPPublicKey) keyIter.next();

                if (key.isEncryptionKey()) {
                    return key;
                }
            }
        }

        throw new IllegalArgumentException("Can't find encryption key in key ring.");
    }
    
    public static void decryptFile(String inputFileName, String keyFileName, String password, String defaultFileName)
            throws Exception {
        InputStream in = null;
        InputStream keyIn = null;
        try {
            in = new BufferedInputStream(new FileInputStream(inputFileName));
            keyIn = new BufferedInputStream(new FileInputStream(keyFileName));
            decryptFile(in, keyIn, password.toCharArray(), defaultFileName);
        } finally {
            if(in!=null) {
                in.close();
            }
            if(keyIn!=null) {
                keyIn.close();
            }
        }
    }
    
    @SuppressWarnings("rawtypes")
    public static void decryptFile(InputStream in, InputStream keyIn, char[] passwd, String defaultFileName)
            throws Exception {
        in = PGPUtil.getDecoderStream(in);

        try {
            PGPObjectFactory pgpF = new PGPObjectFactory(in);
            PGPEncryptedDataList enc;

            Object o = pgpF.nextObject();
            //
            // the first object might be a PGP marker packet.
            //
            if (o instanceof PGPEncryptedDataList) {
                enc = (PGPEncryptedDataList) o;
            } else {
                enc = (PGPEncryptedDataList) pgpF.nextObject();
            }

            //
            // find the secret key
            //
            Iterator it = enc.getEncryptedDataObjects();
            PGPPrivateKey sKey = null;
            PGPPublicKeyEncryptedData pbe = null;
            PGPSecretKeyRingCollection pgpSec = new PGPSecretKeyRingCollection(PGPUtil.getDecoderStream(keyIn));

            while (sKey == null && it.hasNext()) {
                pbe = (PGPPublicKeyEncryptedData) it.next();

                sKey = findSecretKey(pgpSec, pbe.getKeyID(), passwd);
            }

            if (sKey == null) {
                throw new IllegalArgumentException("secret key for message not found.");
            }

            InputStream clear = pbe
                    .getDataStream(new JcePublicKeyDataDecryptorFactoryBuilder().setProvider("BC").build(sKey));

            PGPObjectFactory plainFact = new PGPObjectFactory(clear);

            Object message = plainFact.nextObject();

            if (message instanceof PGPCompressedData) {
                PGPCompressedData cData = (PGPCompressedData) message;
                PGPObjectFactory pgpFact = new PGPObjectFactory(cData.getDataStream());

                message = pgpFact.nextObject();
            }

            if (message instanceof PGPLiteralData) {
                PGPLiteralData ld = (PGPLiteralData) message;

                String outFileName = ld.getFileName();
//                if (outFileName.length() == 0) {
//                    outFileName = defaultFileName;
//                }
                outFileName = defaultFileName;

                InputStream unc = ld.getInputStream();
                OutputStream fOut = new BufferedOutputStream(new FileOutputStream(outFileName));

                Streams.pipeAll(unc, fOut);

                fOut.close();
            } else if (message instanceof PGPOnePassSignatureList) {
                throw new PGPException("encrypted message contains a signed message - not literal data.");
            } else {
                throw new PGPException("message is not a simple encrypted file - type unknown.");
            }

            if (pbe.isIntegrityProtected()) {
                if (!pbe.verify()) {
                    System.err.println("message failed integrity check");
                } else {
                    System.err.println("message integrity check passed");
                }
            } else {
                System.err.println("no message integrity check");
            }
        } catch (PGPException e) {
            System.err.println(e);
            if (e.getUnderlyingException() != null) {
                e.getUnderlyingException().printStackTrace();
            }
            throw e;
        }
    }

    public static PGPPrivateKey findSecretKey(PGPSecretKeyRingCollection pgpSec, long keyID, char[] pass)
            throws PGPException, NoSuchProviderException {
        PGPSecretKey pgpSecKey = pgpSec.getSecretKey(keyID);

        if (pgpSecKey == null) {
            return null;
        }

        return pgpSecKey.extractPrivateKey(new JcePBESecretKeyDecryptorBuilder().setProvider("BC").build(pass));
    }
}

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