Android 平台如何使用 RSA 算法进行加解密？

import java.lang.StringBuilderimport java.lang.reflect.Constructorimport java.security.*import java.security.interfaces.RSAPrivateKeyimport java.security.interfaces.RSAPublicKeyimport java.security.spec.PKCS8EncodedKeySpecimport java.security.spec.X509EncodedKeySpecimport javax.crypto.Cipher
class RSAUtil private constructor(){    companion object{        @Volatile        private var instance: RSAUtil? = null        private val instanceLock = Any()
        fun getInstance(): RSAUtil {            val tmp = instance            if (tmp != null) {                return tmp            }
            synchronized(instanceLock) {                if (instance == null) {                    instance = RSAUtil()                }                return instance!!            }        }    }
    private val keyPair : KeyPair = generateRSAKeyPair(1024)
    fun getPublicKey(): ByteArray {        val rsaPublicKey: RSAPublicKey = keyPair.public as RSAPublicKey        return rsaPublicKey.encoded    }
    fun getPrivateKey(): ByteArray {        val rsaPrivateKey: RSAPrivateKey = keyPair.private as RSAPrivateKey        return rsaPrivateKey.encoded    }}
/**RSA算法 */val RSA = "RSA"/**加密方式，android的*///  public static final String TRANSFORMATION = "RSA/None/NoPadding";/**加密方式，android的 *///  public static final String TRANSFORMATION = "RSA/None/NoPadding";/**加密方式，标准jdk的 */val TRANSFORMATION = "RSA/None/PKCS1Padding"
/** 生成密钥对，即公钥和私钥。key长度是512-2048，一般为1024  */@Throws(NoSuchAlgorithmException::class)fun generateRSAKeyPair(keyLength: Int): KeyPair {    val kpg: KeyPairGenerator = KeyPairGenerator.getInstance(RSA)    kpg.initialize(keyLength)    return kpg.genKeyPair()}/** 获取公钥，打印为48-12613448136942-12272-122-913111503-126115048-12...等等一长串用-拼接的数字  */fun getPublicKey(keyPair: KeyPair): ByteArray {    val rsaPublicKey: RSAPublicKey = keyPair.public as RSAPublicKey    return rsaPublicKey.encoded}
/** 获取私钥，同上  */fun getPrivateKey(keyPair: KeyPair): ByteArray {    val rsaPrivateKey: RSAPrivateKey = keyPair.private as RSAPrivateKey    return rsaPrivateKey.encoded}
/** 使用公钥加密  */@Throws(Exception::class)fun encryptByPublicKey(data: ByteArray?, publicKey: ByteArray?): ByteArray? {    // 得到公钥对象    val keySpec = X509EncodedKeySpec(publicKey)    val keyFactory: KeyFactory = KeyFactory.getInstance("RSA")    val pubKey: PublicKey = keyFactory.generatePublic(keySpec)    // 加密数据    val cp: Cipher = Cipher.getInstance(TRANSFORMATION)    cp.init(Cipher.ENCRYPT_MODE, pubKey)    return cp.doFinal(data)}
/** 使用私钥解密  */@Throws(Exception::class)fun decryptByPrivateKey(encrypted: ByteArray?, privateKey: ByteArray?): ByteArray? {    // 得到私钥对象    val keySpec = PKCS8EncodedKeySpec(privateKey)    val kf: KeyFactory = KeyFactory.getInstance(RSA)    val keyPrivate: PrivateKey = kf.generatePrivate(keySpec)    // 解密数据    val cp: Cipher = Cipher.getInstance(TRANSFORMATION)    cp.init(Cipher.DECRYPT_MODE, keyPrivate)    return cp.doFinal(encrypted)}
fun byteArray2String(bytes: ByteArray?): String? {    if (null == bytes) return null    val stringBuffer = StringBuilder()    for (byte in bytes) {        stringBuffer.append(byte)    }    return stringBuffer.toString()}

import com.nufront.trunking.common.system.LogUtilimport java.nio.charset.Charsetimport java.security.KeyPair
fun test() {    val data = "hello world123321"    try {        val keyLength = 1024        //生成密钥对        val keyPair: KeyPair = generateRSAKeyPair(keyLength)        //获取公钥        val publicKey: ByteArray = getPublicKey(keyPair)        //获取私钥        val privateKey: ByteArray = getPrivateKey(keyPair)
        //用公钥加密        val encrypt = encryptByPublicKey(data.toByteArray(), publicKey)        LogUtil.e("cclin", "加密后的数据：" + byteArray2String(encrypt))
        //用私钥解密        val decrypt = decryptByPrivateKey(encrypt, privateKey)        LogUtil.e("cclin", "解密后的数据：" + String(decrypt!!, Charset.defaultCharset()))    } catch (e: Exception) {        e.printStackTrace()        LogUtil.printException(e)    }}