一、对称加密算法
加密和解密使用相同密钥的加密算法。常用的算法包括DES、3DES、AES、DESX、Blowfish、RC4、RC5、RC6。
DES（Data Encryption Standard）：数据加密标准，速度较快，适用于加密大量数据的场合。
3DES（Triple DES）：是基于DES，对一块数据用三个不同的密钥进行三次加密，强度更高。
AES（Advanced Encryption Standard）：高级加密标准，速度快，安全级别高【128位秘钥】；
二、非对称加密算法
加密和解密使用不同密钥的加密算法，也称为公私钥加密。常见的算法包括RSA、DSA（数字签名用）、ECC（移动设备用）、Diffie-Hellman、El Gamal。
RSA：由 RSA 公司发明，是一个支持变长密钥的公共密钥算法，需要加密的文件块的长度也是可变的；【建议1024位秘钥】
DSA：数字签名算法，是一种标准的 DSS（数字签名标准）
ECC：椭圆曲线密码编码学【建议160位秘钥】。
ECC VS RSA
1）抗攻击性强。相同的密钥长度，其抗攻击性要强很多倍。
2）计算量小，处理速度快。ECC总的速度比RSA、DSA要快得多。
3）存储空间占用小。ECC的密钥尺寸和系统参数与RSA、DSA相比要小得多，意味着它所占的存贮空间要小得多。这对于加密算法在IC卡上的应用具有特别重要的意义。
4）带宽要求低。当对长消息进行加解密时，三类密码系统有相同的带宽要求，但应用于短消息时ECC带宽要求却低得多。带宽要求低使ECC在无线网络领域具有广泛的应用前景。
三、散列算法
除法散列法 平方散列法 斐波那契（Fibonacci）散列法 随机数法
单向散列函数一般用于产生消息摘要，密钥加密等，常用的算法包括MD2、MD4、MD5、HAVAL、SHA、SHA-1、HMAC、HMAC-MD5、HMAC-SHA1。
MD5（Message Digest Algorithm 5）：是RSA数据安全公司开发的一种单向散列算法，非可逆，相同的明文产生相同的密文。
SHA（Secure Hash Algorithm）：可以对任意长度的数据运算生成一个160位的数值；
SHA-1 VS MD5 [二者均由MD4导出]
1）SHA-1摘要比MD5摘要长32位。使用强行技术，产生任何一个报文使其摘要等于给定报摘要的难度对MD5是2^(128)数量级的操作，而对SHA-1则是2^(160)数量级的操作。这样，SHA-1对强行攻击有更大的强度。
2）MD5易受密码分析的攻击，SHA-1显得不易受这样的攻击。
3）在相同的硬件上，SHA-1的运行速度比MD5慢。
四、加密算法的选择
单方密码存储建议直接使用散列算法（MD5即可，配合密码更新策略）。
内部信息加密传输建议使用对称加密效率跟高（AES）。
外部数据传输建议使用非对称加密，秘钥保存更安全（RSA）。
HTTPS高级用法：采用非对称加密算法管理对称算法的密钥，然后用对称加密算法加密数据，这样我们就集成了两类加密算法的优点，既实现了加密速度快的优点，又实现了安全方便管理密钥的优点。
五、上源码
5.1 AES对称加密
import lombok.extern.slf4j.Slf4j;import org.apache.commons.codec.binary.Base64;import org.apache.commons.lang3.ArrayUtils;import org.springframework.util.StringUtils;import javax.crypto.Cipher;import javax.crypto.SecretKey;import javax.crypto.spec.SecretKeySpec;import java.nio.charset.StandardCharsets;@Slf4jpublic class AESUtils { // 秘钥 16 private static final String SECRET_KEY = "1111111111111111"; // 秘钥 24 //private static final String SECRET_KEY = "111111111111111122222222"; // 秘钥 32 //private static final String SECRET_KEY = "11111111111111112222222233333333"; // 算法 private static final String ALGORITHM = "AES"; private static final String UTF8 = StandardCharsets.UTF_8.name(); public static String encryption(String message, String secretKey) { if (!StringUtils.hasLength(message)) { log.error("encryption message should not be null or empty."); } byte[] encodeBytes = encryption(message.getBytes(StandardCharsets.UTF_8), secretKey); return Base64.encodeBase64String(encodeBytes); } public static byte[] encryption(byte[] messageBytes, String secretKey) { if (ArrayUtils.isEmpty(messageBytes)) { log.error("encryption message should not be empty."); } if (!StringUtils.hasLength(secretKey)) { log.error("secretKey {}, encryption key should not be null or empty.", secretKey); } Cipher cipher = getCipher(secretKey, Cipher.ENCRYPT_MODE); byte[] encryptionBytes = null; try { encryptionBytes = cipher.doFinal(messageBytes); } catch (Exception e) { log.error("encryption fail. ", e); } return encryptionBytes; } public static String decrypt(String encryptionMessage, String secretKey) { if (!StringUtils.hasLength(encryptionMessage)) { log.error("decrypt encryptionMessage should not be null or empty."); } byte[] decodeBytes = decrypt(Base64.decodeBase64(encryptionMessage.getBytes(StandardCharsets.UTF_8)), secretKey); return new String(decodeBytes, StandardCharsets.UTF_8); } public static byte[] decrypt(byte[] encryptedBytes, String secretKey) { if (ArrayUtils.isEmpty(encryptedBytes)) { log.error("decrypt encryptedBytes should not be empty."); } if (!StringUtils.hasLength(secretKey)) { log.error("secretKey {}, decrypt key should not be null or empty.", secretKey); } Cipher cipher = getCipher(secretKey, Cipher.DECRYPT_MODE); byte[] decodeBytes = null; try { decodeBytes = cipher.doFinal(encryptedBytes); } catch (Exception e) { log.error("decrypt fail. ", e); } return decodeBytes; } private static Cipher getCipher(String key, int mode) { Cipher cipher = null; SecretKey secretKey; try { cipher = Cipher.getInstance(ALGORITHM); byte[] keyBytes = key.getBytes(UTF8); secretKey = new SecretKeySpec(keyBytes, ALGORITHM); cipher.init(mode, secretKey); } catch (Exception e) { log.error("getAESCipher fail. ", e); } return cipher; } public static void main(String[] args) { String data = "ocean测试!@#"; log.info("AES秘钥长度只能为16、24、32:{}", SECRET_KEY.getBytes(StandardCharsets.UTF_8).length); String encryptionData = encryption(data, SECRET_KEY); log.info("加密后:{}", encryptionData); String decryptData = decrypt(encryptionData, SECRET_KEY); log.info("解密后:{}", decryptData); }}5.2 RSA非对称加密
PSCK#8 - PSCK#1org.bouncycastle bcprov-jdk15on 1.52 import java.io.StringWriter;import java.security.KeyFactory;import java.security.KeyPair;import java.security.KeyPairGenerator;import java.security.NoSuchAlgorithmException;import java.security.PrivateKey;import java.security.PublicKey;import java.security.Signature;import java.security.interfaces.RSAPrivateKey;import java.security.interfaces.RSAPublicKey;import java.security.spec.InvalidKeySpecException;import java.security.spec.PKCS8EncodedKeySpec;import java.security.spec.X509EncodedKeySpec;import java.util.HashMap;import java.util.Map;import javax.crypto.Cipher;import org.apache.commons.codec.binary.Base64;import org.bouncycastle.asn1.ASN1Encodable;import org.bouncycastle.asn1.ASN1Primitive;import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;import org.bouncycastle.util.io.pem.PemObject;import org.bouncycastle.util.io.pem.PemWriter;import sun.misc.BASE64Decoder;import sun.misc.BASE64Encoder;public class RsaUtils {public static final int KEY_SIZE = 2048;public static final String ALGORITHM = "RSA";public static final String PUBLIC_KEY = "xxxxpublicKeyxxxx";public static final String PRIVATE_KEY = "xxxxprivateKeyxxxx";public static final String CLEAR_TEXT_STRING = "明文字符串";public static BASE64Encoder encoder = new BASE64Encoder();public static BASE64Decoder decoder = new BASE64Decoder();public static void main(String[] args) throws Exception {// PSCK#8Map keyMap = RsaUtil.generateKeyBytes();System.out.println("PSCK#8-PRIVATEKEY:"+ keyMap.get(RsaUtil.PRIVATE_KEY));System.out.println("PSCK#8-PUBLICKEY:" + keyMap.get(RsaUtil.PUBLIC_KEY));PublicKey publicKey8 = RsaUtil.restorePublicKey(keyMap.get(RsaUtil.PUBLIC_KEY));PrivateKey privateKey8 = RsaUtil.restorePrivateKey(keyMap.get(RsaUtil.PRIVATE_KEY));// ============公钥加密-私钥解密============Cipher cipher = Cipher.getInstance(ALGORITHM);cipher.init(Cipher.ENCRYPT_MODE, publicKey8);String messageEn = Base64.encodeBase64String(cipher.doFinal(CLEAR_TEXT_STRING.getBytes("UTF-8")));System.out.println(CLEAR_TEXT_STRING + "\t加密后的字符串为:" + messageEn);cipher.init(Cipher.DECRYPT_MODE, privateKey8);String messageDe = new String(cipher.doFinal(Base64.decodeBase64(messageEn.getBytes("UTF-8"))));System.out.println("还原后的字符串为:" + messageDe);// ============公钥加密-私钥解密============// ============PSCK#8>PSCK#1============byte[] privBytes = privateKey8.getEncoded();PrivateKeyInfo pkInfo = PrivateKeyInfo.getInstance(privBytes);ASN1Encodable encodable = pkInfo.getPrivateKey();ASN1Primitive primitive = encodable.toASN1Primitive();byte[] privateKeyPKCS1 = primitive.getEncoded();PemObject pemObject = new PemObject("RSA PRIVATE KEY", privateKeyPKCS1);StringWriter stringWriter = new StringWriter();PemWriter pemWriter = new PemWriter(stringWriter);pemWriter.writeObject(pemObject);pemWriter.close();String pemString = stringWriter.toString();System.out.println("PSCK#1-PRIVATEKEY:" + pemString);byte[] pubBytes = publicKey8.getEncoded();SubjectPublicKeyInfo spkInfo = SubjectPublicKeyInfo.getInstance(pubBytes);ASN1Primitive punlic = spkInfo.parsePublicKey();byte[] publicKeyPKCS1 = punlic.getEncoded();PemObject punlicpemObject = new PemObject("RSA PUBLIC KEY",publicKeyPKCS1);StringWriter punlicstringWriter = new StringWriter();PemWriter punlicpemWriter = new PemWriter(punlicstringWriter);punlicpemWriter.writeObject(punlicpemObject);punlicpemWriter.close();String publicemString = punlicstringWriter.toString();System.out.println("PSCK#8-PUBLICKEY:" + publicemString);// ============PSCK#8>PSCK#1============// ============私钥签名公钥验签============// PSCK#8-PRIVATEKEY 私钥签名Signature signature = Signature.getInstance("SHA256WithRSA");signature.initSign(privateKey8);signature.update(CLEAR_TEXT_STRING.getBytes());byte[] signed = signature.sign();String sign = encoder.encode(signed);// PSCK#8-PUBLICKEY 公钥验签signature.initVerify(publicKey8);signature.update(CLEAR_TEXT_STRING.getBytes());boolean verify = signature.verify(decoder.decodeBuffer(sign));System.out.println("CLEAR_TEXT_STRING:" + CLEAR_TEXT_STRING);System.out.println("SIGN:" + sign.replaceAll("\r|\n", ""));System.out.println(verify);// ============私钥签名公钥验签============}public static Map generateKeyBytes() {try {KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);keyPairGenerator.initialize(KEY_SIZE);KeyPair keyPair = keyPairGenerator.generateKeyPair();RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();Map keyMap = new HashMap();keyMap.put(PUBLIC_KEY, new String(Base64.encodeBase64(publicKey.getEncoded())));keyMap.put(PRIVATE_KEY, new String(Base64.encodeBase64(privateKey.getEncoded())));return keyMap;} catch (NoSuchAlgorithmException e) {e.printStackTrace();}return null;}public static PublicKey restorePublicKey(String key) {X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(Base64.decodeBase64(key));try {KeyFactory factory = KeyFactory.getInstance(ALGORITHM);PublicKey publicKey = factory.generatePublic(x509EncodedKeySpec);return publicKey;} catch (NoSuchAlgorithmException | InvalidKeySpecException e) {e.printStackTrace();}return null;} public static PrivateKey restorePrivateKey(String key) { PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(key)); try { KeyFactory factory = KeyFactory.getInstance(ALGORITHM); PrivateKey privateKey = factory .generatePrivate(pkcs8EncodedKeySpec); return privateKey; } catch (NoSuchAlgorithmException | InvalidKeySpecException e) { e.printStackTrace(); } return null; }} 5.3 MD5散列算法
import lombok.extern.slf4j.Slf4j;import java.security.MessageDigest;@Slf4jpublic class MD5Util { public static final int SIZE_FACTOR = 2; private static final String[] hexDigits = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"}; public static String MD5Encode(String origin, String charsetname) { String resultString = null; try { resultString = origin; MessageDigest md = MessageDigest.getInstance("MD5"); if (charsetname == null || "".equals(charsetname)) { resultString = byteArrayToHexString(md.digest(resultString.getBytes())); } else { resultString = byteArrayToHexString(md.digest(resultString.getBytes(charsetname))); } } catch (Exception exception) { log.error("MD5Util MD5Encode error", exception); } return resultString; } private static String byteArrayToHexString(byte[] b) { StringBuffer resultSb = new StringBuffer(); for (int i = 0; i < b.length; i++) { resultSb.append(byteToHexString(b[i])); } return resultSb.toString(); } private static String byteToHexString(byte b) { int n = b; if (n < 0) { n += 256; } int d1 = n / 16; int d2 = n % 16; return hexDigits[d1] + hexDigits[d2]; } public static String encode(String str) { try { byte[] hash = MessageDigest.getInstance("MD5").digest(str.getBytes("utf-8")); StringBuilder hex = new StringBuilder(hash.length * SIZE_FACTOR); for (byte b : hash) { hex.append(String.format("%02x", b)); } return hex.toString(); } catch (Exception e) { log.error("MD5 encode error for {}, error is {}", str, e.getMessage(), e); } return null; }}来源地址：https://blog.csdn.net/qq_34253002/article/details/131491945
