android rsa 加密

android rsa 加密

import java.io.ByteArrayOutputStream
import java.security.KeyFactory
import java.security.KeyPairGenerator
import java.security.PrivateKey
import java.security.PublicKey
import java.security.spec.PKCS8EncodedKeySpec
import java.security.spec.X509EncodedKeySpec
import javax.crypto.Cipher
import kotlin.io.encoding.Base64

object RSACrypt {
//    const val TRANSFORMATION = "RSA"
    const val TRANSFORMATION = "RSA/ECB/PKCS1Padding"
    const val ENCRYPT_MAX_SIZE = 117//每次最大加密长度
    const val DECRYPT_MAX_SIZE = 128//每次最大解密长度

    fun getPrivateKey(privateKeyStr: String): PrivateKey {
        return KeyFactory.getInstance("RSA").generatePrivate(PKCS8EncodedKeySpec(Base64.decode(privateKeyStr)))

    }
    fun getPublicKey(publicKeyStr: String): PublicKey {
        return KeyFactory.getInstance("RSA").generatePublic(X509EncodedKeySpec(Base64.decode(publicKeyStr)))
    }

    /**
     * 私钥分段加密
     * @param input 原文
     * @param privateKeyStr 私钥
     */
    fun encryptByPrivateKey(input: String, privateKeyStr: String): String {

        val privateKey: PrivateKey = getPrivateKey(privateKeyStr)
        val byteArray = input.toByteArray()

        //创建cipher对象
        val cipher = Cipher.getInstance(TRANSFORMATION)
        //初始化cipher
        cipher.init(Cipher.ENCRYPT_MODE, privateKey)
        //分段加密
        var temp: ByteArray? = null
        var offset = 0//当前偏移位置
        val bos = ByteArrayOutputStream()
        while (byteArray.size - offset > 0) {  //没有加密完成
            //每次加密245个字节
            if (byteArray.size - offset >= ENCRYPT_MAX_SIZE) {
                //剩余部分大于245
                //bytearray，偏移，加密245个字节
                temp = cipher.doFinal(byteArray, offset, ENCRYPT_MAX_SIZE)
                //重新计算offset
                offset += ENCRYPT_MAX_SIZE
            } else {
                temp = cipher.doFinal(byteArray, offset, byteArray.size - offset)
                offset = byteArray.size
            }
            //存储到临时缓冲区
            bos.write(temp)
        }
        bos.close()
        return Base64.encode(bos.toByteArray())
    }

    /**
     * 公钥分段加密
     * @param input 原文
     * @param publicKeyStr 公钥
     */
    fun encryptByPublicKey(input: String, publicKeyStr: String): String {

        val publicKey = getPublicKey(publicKeyStr)
        val byteArray = input.toByteArray()

        val cipher = Cipher.getInstance(TRANSFORMATION)
        cipher.init(Cipher.ENCRYPT_MODE, publicKey)

        var temp: ByteArray? = null
        var offset = 0//当前偏移位置
        val bos = ByteArrayOutputStream()
        while (byteArray.size - offset > 0) {  //没有加密完成
            if (byteArray.size - offset >= ENCRYPT_MAX_SIZE) {
                temp = cipher.doFinal(byteArray, offset, ENCRYPT_MAX_SIZE)
                offset += ENCRYPT_MAX_SIZE
            } else {
                temp = cipher.doFinal(byteArray, offset, byteArray.size - offset)
                offset = byteArray.size
            }
            bos.write(temp)
        }
        bos.close()
        return Base64.encode(bos.toByteArray())
    }

    /**
     * 公钥分段解密
     * @param input 密文
     * @param publicKeyStr 公钥
     */
    fun decryptByPublicKey(input: String, publicKeyStr: String): String {
        val publicKey = getPublicKey(publicKeyStr)
        val byteArray = Base64.decode(input)

        val cipher = Cipher.getInstance(TRANSFORMATION)
        cipher.init(Cipher.DECRYPT_MODE, publicKey)

        var temp: ByteArray? = null
        var offset = 0//当前偏移位置
        val bos = ByteArrayOutputStream()
        while (byteArray.size - offset > 0) {  //没有解密完成
            if (byteArray.size - offset >= DECRYPT_MAX_SIZE) {
                temp = cipher.doFinal(byteArray, offset, DECRYPT_MAX_SIZE)
                offset += DECRYPT_MAX_SIZE
            } else {
                temp = cipher.doFinal(byteArray, offset, byteArray.size - offset)
                offset = byteArray.size
            }
            bos.write(temp)
        }
        bos.close()
        return String(bos.toByteArray())
    }

    /**
     * 私钥分段解密
     * @param input 密文
     * @param privateKeyStr 私钥
     */
    fun decryptByPrivateKey(input: String, privateKeyStr: String): String {

        val privateKey: PrivateKey = getPrivateKey(privateKeyStr)
        val byteArray = Base64.decode(input)

        val cipher = Cipher.getInstance(TRANSFORMATION)
        cipher.init(Cipher.DECRYPT_MODE, privateKey)

        var temp: ByteArray? = null
        var offset = 0//当前偏移位置
        val bos = ByteArrayOutputStream()
        while (byteArray.size - offset > 0) {  //没有解密完成
            if (byteArray.size - offset >= DECRYPT_MAX_SIZE) {
                temp = cipher.doFinal(byteArray, offset, DECRYPT_MAX_SIZE)
                offset += DECRYPT_MAX_SIZE
            } else {
                temp = cipher.doFinal(byteArray, offset, byteArray.size - offset)
                offset = byteArray.size
            }
            bos.write(temp)
        }
        bos.close()
        return String(bos.toByteArray())
    }


}

fun generateKey(){
    //如何生成密钥对
    val generator = KeyPairGenerator.getInstance("RSA")
    generator.initialize(1024)
    val keyPair = generator.genKeyPair()//声明密钥对
    val publicKey = keyPair.public//公钥
    val privateKey = keyPair.private//私钥

    println("publicKey="+ Base64.encode(publicKey.encoded))
    println("privateKey="+Base64.encode(privateKey.encoded))
}

val encryptByPublicKey = RSACrypt.encryptByPrivateKey(input, privateKeyStr)
    println("encryptByPublicKey:$encryptByPublicKey")
    val decryptByPrivateKey = RSACrypt.decryptByPublicKey(encryptByPublicKey, publicKeyStr)
    println("decryptByPrivateKey2:$decryptByPrivateKey")

 

参考：https://www.jianshu.com/p/485dee91ac19