背景：

使用公钥加密数据，然后使用私钥解密。网上找的现成的java方法，然后转成kotlin。

import org.apache.commons.codec.binary.Base64
import java.security.KeyFactory
import java.security.KeyPairGenerator
import java.security.PrivateKey
import java.security.PublicKey
import java.security.interfaces.RSAPrivateKey
import java.security.interfaces.RSAPublicKey
import java.security.spec.PKCS8EncodedKeySpec
import java.security.spec.X509EncodedKeySpec
import java.time.LocalDate
import javax.crypto.Cipher

/**
 * @Author: anson
 * @Date: 2022/2/4 4:02 PM
 */
object RSAUtils {

    /**
     * 公钥加密私钥解密
     */
    fun test1(keyPair: RSAKeyPair, source: String) {
        println("***************** 公钥加密私钥解密开始 *****************")
        println("加密前：$source")
        val text1 = encryptByPublicKey(keyPair.publicKey, source)
        println("加密后：$text1")
        val text2 = decryptByPrivateKey(keyPair.privateKey, text1)
        println("解密后：$text2")
        if (source == text2) {
            println("解密字符串和原始字符串一致，解密成功")
        } else {
            println("解密字符串和原始字符串不一致，解密失败")
        }
        println("***************** 公钥加密私钥解密结束 *****************")
    }

    /**
     * 私钥加密公钥解密
     *
     * @throws Exception
     */
    fun test2(keyPair: RSAKeyPair, source: String) {
        println("***************** 私钥加密公钥解密开始 *****************")
        val text1 = encryptByPrivateKey(keyPair.privateKey, source)
        val text2 = decryptByPublicKey(keyPair.publicKey, text1)
        println("加密前：$source")
        println("加密后：$text1")
        println("解密后：$text2")
        if (source == text2) {
            println("解密字符串和原始字符串一致，解密成功")
        } else {
            println("解密字符串和原始字符串不一致，解密失败")
        }
        println("***************** 私钥加密公钥解密结束 *****************")
    }

    /**
     * 公钥解密
     *
     * @param publicKeyText
     * @param text
     * @return
     */
    fun decryptByPublicKey(publicKeyText: String, text: String): String {
        val x509EncodedKeySpec = X509EncodedKeySpec(Base64.decodeBase64(publicKeyText))
        val keyFactory: KeyFactory = KeyFactory.getInstance("RSA")
        val publicKey: PublicKey = keyFactory.generatePublic(x509EncodedKeySpec)
        val cipher: Cipher = Cipher.getInstance("RSA")
        cipher.init(Cipher.DECRYPT_MODE, publicKey)
        val result: ByteArray = cipher.doFinal(Base64.decodeBase64(text))
        return String(result)
    }

    /**
     * 私钥加密
     *
     * @param privateKeyText
     * @param text
     */
    fun encryptByPrivateKey(privateKeyText: String, text: String): String {
        val pkcs8EncodedKeySpec = PKCS8EncodedKeySpec(Base64.decodeBase64(privateKeyText))
        val keyFactory: KeyFactory = KeyFactory.getInstance("RSA")
        val privateKey: PrivateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec)
        val cipher: Cipher = Cipher.getInstance("RSA")
        cipher.init(Cipher.ENCRYPT_MODE, privateKey)
        val result: ByteArray = cipher.doFinal(text.toByteArray())
        return Base64.encodeBase64String(result)
    }

    /**
     * 私钥解密
     *
     * @param privateKeyText
     * @param text
     * @return
     * @throws Exception
     */
    fun decryptByPrivateKey(privateKeyText: String, text: String): String {
        val pkcs8EncodedKeySpec5 = PKCS8EncodedKeySpec(Base64.decodeBase64(privateKeyText))
        val keyFactory: KeyFactory = KeyFactory.getInstance("RSA")
        val privateKey: PrivateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec5)
        val cipher: Cipher = Cipher.getInstance("RSA")
        cipher.init(Cipher.DECRYPT_MODE, privateKey)
        val result: ByteArray = cipher.doFinal(Base64.decodeBase64(text))
        return String(result)
    }

    /**
     * 公钥加密
     *
     * @param publicKeyText
     * @param text
     * @return
     */
    fun encryptByPublicKey(publicKeyText: String, text: String): String {
        val x509EncodedKeySpec2 = X509EncodedKeySpec(Base64.decodeBase64(publicKeyText))
        val keyFactory: KeyFactory = KeyFactory.getInstance("RSA")
        val publicKey: PublicKey = keyFactory.generatePublic(x509EncodedKeySpec2)
        val cipher: Cipher = Cipher.getInstance("RSA")
        cipher.init(Cipher.ENCRYPT_MODE, publicKey)
        val result: ByteArray = cipher.doFinal(text.toByteArray())
        return Base64.encodeBase64String(result)
    }

    /**
     * 构建RSA密钥对
     *
     */
    fun generateKeyPair(): RSAKeyPair {
        val keyPairGenerator = KeyPairGenerator.getInstance("RSA")
        keyPairGenerator.initialize(512)
        val keyPair = keyPairGenerator.generateKeyPair()
        val rsaPublicKey = keyPair.public as RSAPublicKey
        val rsaPrivateKey = keyPair.private as RSAPrivateKey
        val publicKeyString: String = Base64.encodeBase64String(rsaPublicKey.encoded)
        val privateKeyString: String = Base64.encodeBase64String(rsaPrivateKey.encoded)
        return RSAKeyPair(publicKeyString, privateKeyString)
    }

    /**
     * RSA密钥对对象
     */
    data class RSAKeyPair(val publicKey: String, val privateKey: String)

}