package com.example.firstapp.utils
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import java.io.ByteArrayOutputStream
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import java.security.KeyFactory
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import java.security.PrivateKey
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import java.security.PublicKey
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import java.security.spec.PKCS8EncodedKeySpec
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import java.security.spec.X509EncodedKeySpec
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import javax.crypto.Cipher
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/**
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* 非对称加密RSA加密和解密
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*/
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object RSACrypt {
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private const val TRANSFORMATION = "RSA"
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private const val ENCRYPT_MAX_SIZE = 245
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private const val DECRYPT_MAX_SIZE = 256
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/**
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* 私钥加密
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* @param input 原文
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* @param privateKey 私钥
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*/
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fun encryptByPrivateKey(input: String, privateKey: PrivateKey): String {
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//创建cipher对象
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val cipher = Cipher.getInstance(TRANSFORMATION)
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//初始化cipher
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cipher.init(Cipher.ENCRYPT_MODE, privateKey)
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//****非对称加密****
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val byteArray = input.toByteArray()
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//分段加密
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var temp: ByteArray?
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var offset = 0 //当前偏移的位置
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val outputStream = ByteArrayOutputStream()
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//拆分input
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while (byteArray.size - offset > 0) {
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//每次最大加密245个字节
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if (byteArray.size - offset >= ENCRYPT_MAX_SIZE) {
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//剩余部分大于245
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//加密完整245
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temp = cipher.doFinal(byteArray, offset, ENCRYPT_MAX_SIZE)
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//重新计算偏移位置
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offset += ENCRYPT_MAX_SIZE
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} else {
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//加密最后一块
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temp = cipher.doFinal(byteArray, offset, byteArray.size - offset)
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//重新计算偏移位置
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offset = byteArray.size
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}
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//存储到临时的缓冲区
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outputStream.write(temp)
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}
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outputStream.close()
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return Base64.encode(outputStream.toByteArray())
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}
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/**
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* 公钥加密
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* @param input 原文
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* @param publicKey 公钥
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*/
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fun encryptByPublicKey(input: String, publicKey: PublicKey): String {
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//创建cipher对象
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val cipher = Cipher.getInstance(TRANSFORMATION)
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//初始化cipher
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cipher.init(Cipher.ENCRYPT_MODE, publicKey)
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//****非对称加密****
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val byteArray = input.toByteArray()
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var temp: ByteArray?
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var offset = 0 //当前偏移的位置
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val outputStream = ByteArrayOutputStream()
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//拆分input
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while (byteArray.size - offset > 0) {
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//每次最大加密117个字节
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if (byteArray.size - offset >= ENCRYPT_MAX_SIZE) {
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//剩余部分大于117
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//加密完整117
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temp = cipher.doFinal(byteArray, offset, ENCRYPT_MAX_SIZE)
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//重新计算偏移位置
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offset += ENCRYPT_MAX_SIZE
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} else {
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//加密最后一块
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temp = cipher.doFinal(byteArray, offset, byteArray.size - offset)
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//重新计算偏移位置
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offset = byteArray.size
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}
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//存储到临时的缓冲区
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outputStream.write(temp)
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}
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outputStream.close()
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return Base64.encode(outputStream.toByteArray())
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}
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/**
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* 私钥解密
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* @param input 秘文
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* @param privateKey 私钥
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*/
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fun decryptByPrivateKey(input: String, privateKey: PrivateKey): String {
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//创建cipher对象
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val cipher = Cipher.getInstance(TRANSFORMATION)
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//初始化cipher
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cipher.init(Cipher.DECRYPT_MODE, privateKey)
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//****非对称加密****
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val byteArray = Base64.decode(input)
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//分段解密
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var temp: ByteArray?
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var offset = 0 //当前偏移的位置
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val outputStream = ByteArrayOutputStream()
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//拆分input
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while (byteArray.size - offset > 0) {
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//每次最大解密256个字节
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if (byteArray.size - offset >= DECRYPT_MAX_SIZE) {
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temp = cipher.doFinal(byteArray, offset, DECRYPT_MAX_SIZE)
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//重新计算偏移位置
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offset += DECRYPT_MAX_SIZE
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} else {
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//加密最后一块
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temp = cipher.doFinal(byteArray, offset, byteArray.size - offset)
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//重新计算偏移位置
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offset = byteArray.size
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}
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//存储到临时的缓冲区
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outputStream.write(temp)
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}
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outputStream.close()
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return String(outputStream.toByteArray())
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}
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/**
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* 公钥解密
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* @param input 秘文
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* @param publicKey 公钥
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*/
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fun decryptByPublicKey(input: String, publicKey: PublicKey): String {
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//创建cipher对象
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val cipher = Cipher.getInstance(TRANSFORMATION)
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//初始化cipher
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cipher.init(Cipher.DECRYPT_MODE, publicKey)
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//****非对称加密****
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val byteArray = Base64.decode(input)
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//分段解密
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var temp: ByteArray?
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var offset = 0 //当前偏移的位置
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val outputStream = ByteArrayOutputStream()
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//拆分input
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while (byteArray.size - offset > 0) {
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//每次最大解密256个字节
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if (byteArray.size - offset >= DECRYPT_MAX_SIZE) {
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temp = cipher.doFinal(byteArray, offset, DECRYPT_MAX_SIZE)
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//重新计算偏移位置
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offset += DECRYPT_MAX_SIZE
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} else {
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//加密最后一块
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temp = cipher.doFinal(byteArray, offset, byteArray.size - offset)
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//重新计算偏移位置
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offset = byteArray.size
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}
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//存储到临时的缓冲区
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outputStream.write(temp)
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}
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outputStream.close()
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return String(outputStream.toByteArray())
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}
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fun getPrivateKey(privateKeyStr: String): PrivateKey {
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//字符串转成秘钥对对象
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val generator = KeyFactory.getInstance("RSA")
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return generator.generatePrivate(PKCS8EncodedKeySpec(Base64.decode(privateKeyStr)))
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}
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fun getPublicKey(publicKeyStr: String): PublicKey {
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//字符串转成秘钥对对象
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val kf = KeyFactory.getInstance("RSA")
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return kf.generatePublic(X509EncodedKeySpec(Base64.decode(publicKeyStr)))
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}
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}
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