1.什么是PGP算法？
PGP（Pretty Good Privacy）是一种广泛使用的加密和数字签名方案，用于保护电子邮件和文件的安全性。PGP使用对称加密、非对称加密和哈希算法的组合，提供了保密性、完整性和认证的功能。
PGP算法的主要组成部分包括：
1.对称加密：PGP使用对称加密算法（如AES、3DES等）来加密邮件和文件的内容。对称加密使用相同的密钥用于加密和解密，速度较快，适合处理大量数据。
2.非对称加密：PGP使用非对称加密算法（如RSA、ECC等）来加密和解密对称密钥。发送方使用接收方的公钥加密对称密钥，接收方使用自己的私钥解密对称密钥。非对称加密提供了安全的密钥交换和身份验证机制。
3.数字签名：PGP使用数字签名算法（如RSA、DSA等）来对消息进行签名。发送方使用自己的私钥对消息的哈希值进行签名，接收方使用发送方的公钥验证签名的有效性。数字签名提供了消息的完整性和认证。
4.哈希算法：PGP使用哈希算法（如SHA-1、SHA-256等）来计算消息的摘要。哈希算法将消息转换为固定长度的摘要，用于验证消息的完整性和防止篡改。
2.使用Java语言实现SHA算法加密
由于PGP算法较为复杂，我们可以使用Bouncy Castle库来实现PGP算法。可以从Bouncy Castle的官方网站下载到相应的jar包（https://www.bouncycastle.org/）
import org.bouncycastle.bcpg.ArmoredOutputStream; import org.bouncycastle.jce.provider.BouncyCastleProvider; import org.bouncycastle.openpgp.*; import org.bouncycastle.openpgp.operator.jcajce.JcaPGPContentSignerBuilder; import org.bouncycastle.openpgp.operator.jcajce.JcaPGPContentVerifierBuilderProvider; import org.bouncycastle.openpgp.operator.jcajce.JcePGPDataEncryptorBuilder; import org.bouncycastle.openpgp.operator.jcajce.JcePGPDataEncryptorBuilder.AES128; import org.bouncycastle.openpgp.operator.jcajce.JcePGPKeyEncryptionMethodGenerator; import org.bouncycastle.openpgp.operator.jcajce.JcePublicKeyDataDecryptorFactoryBuilder; import org.bouncycastle.openpgp.operator.jcajce.JcePublicKeyKeyEncryptionMethodGenerator; import org.bouncycastle.openpgp.operator.jcajce.JcePublicKeyKeyEncryptionMethodGenerator.AES128_CBC; import org.bouncycastle.openpgp.operator.jcajce.JcePublicKeyKeyEncryptionMethodGenerator.RSA_GENERAL; import org.bouncycastle.util.io.Streams; import java.io.FileInputStream; import java.io.FileOutputStream; import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchProviderException; import java.security.SecureRandom; import java.security.Security; public class PGPExample { public static void main(String[] args) { Security.addProvider(new BouncyCastleProvider()); try { // 生成密钥对 KeyPair keyPair = generateKeyPair(); // 发送方加密文件 String inputFile = "plaintext.txt"; String encryptedFile = "encrypted.pgp"; encryptFile(inputFile, encryptedFile, keyPair.getPublic()); // 接收方解密文件 String decryptedFile = "decrypted.txt"; decryptFile(encryptedFile, decryptedFile, keyPair.getPrivate()); } catch (Exception e) { e.printStackTrace(); } } public static KeyPair generateKeyPair() throws Exception { KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA", "BC"); keyPairGenerator.initialize(2048, new SecureRandom()); return keyPairGenerator.generateKeyPair(); } public static void encryptFile(String inputFile, String outputFile, PGPPublicKey publicKey) throws Exception { FileInputStream inputStream = new FileInputStream(inputFile); FileOutputStream outputStream = new FileOutputStream(outputFile); ArmoredOutputStream armoredOutputStream = new ArmoredOutputStream(outputStream); PGPEncryptedDataGenerator encryptedDataGenerator = new PGPEncryptedDataGenerator(new AES128()); encryptedDataGenerator.addMethod(new JcePublicKeyKeyEncryptionMethodGenerator(publicKey)); OutputStream encryptedOut = encryptedDataGenerator.open(armoredOutputStream, new byte[4096]); PGPCompressedDataGenerator compressedDataGenerator = new PGPCompressedDataGenerator(PGPCompressedDataGenerator.ZIP); OutputStream compressedOut = compressedDataGenerator.open(encryptedOut); PGPUtil.writeFileToLiteralData(compressedOut, PGPLiteralData.BINARY, inputStream, new byte[4096]); compressedOut.close(); compressedDataGenerator.close(); encryptedOut.close(); encryptedDataGenerator.close(); armoredOutputStream.close(); outputStream.close(); inputStream.close(); } public static void decryptFile(String inputFile, String outputFile, PGPSecretKey privateKey) throws Exception { FileInputStream inputStream = new FileInputStream(inputFile); FileOutputStream outputStream = new FileOutputStream(outputFile); PGPObjectFactory objectFactory = new PGPObjectFactory(PGPUtil.getDecoderStream(inputStream), new JcaKeyFingerprintCalculator()); PGPEncryptedDataList encryptedDataList; Object object = objectFactory.nextObject(); if (object instanceof PGPEncryptedDataList) { encryptedDataList = (PGPEncryptedDataList) object; } else { encryptedDataList = (PGPEncryptedDataList) objectFactory.nextObject(); } PGPPublicKeyEncryptedData encryptedData = (PGPPublicKeyEncryptedData) encryptedDataList.get(0); PGPPrivateKey privateKey = findPrivateKey(privateKey, encryptedData.getKeyID(), "password".toCharArray()); InputStream decryptedStream = encryptedData.getDataStream(new JcePublicKeyDataDecryptorFactoryBuilder().setProvider("BC").build(privateKey)); PGPObjectFactory decryptedObjectFactory = new PGPObjectFactory(decryptedStream, new JcaKeyFingerprintCalculator()); Object messageObject = decryptedObjectFactory.nextObject(); if (messageObject instanceof PGPCompressedData) { PGPCompressedData compressedData = (PGPCompressedData) messageObject; PGPObjectFactory decompressedObjectFactory = new PGPObjectFactory(compressedData.getDataStream(), new JcaKeyFingerprintCalculator()); messageObject = decompressedObjectFactory.nextObject(); } PGPLiteralData literalData = (PGPLiteralData) messageObject; InputStream literalDataStream = literalData.getInputStream(); Streams.pipeAll(literalDataStream, outputStream); literalDataStream.close(); outputStream.close(); decryptedStream.close(); inputStream.close(); } public static PGPPrivateKey findPrivateKey(PGPSecretKey secretKey, long keyID, char[] passPhrase) throws PGPException, NoSuchProviderException { PBESecretKeyDecryptor decryptor = new JcePBESecretKeyDecryptorBuilder().setProvider("BC").build(passPhrase); return secretKey.extractPrivateKey(decryptor); } }
该示例展示了如何使用Bouncy Castle库来实现PGP算法。它包括生成密钥对、使用公钥加密文件和使用私钥解密文件的示例代码。在实际应用中，还需要适当处理异常和错误情况，并根据具体需求进行适当的配置和调整。
