Android加密算法之RSA(二) The RSA algorithm can only encrypt data that has a maximum byte length of the RSA key length in bits divided with eight minus eleven padding bytes, i.e. number of maximum bytes = key length in bits / 8 - 11.使用RSA时，数据过长会报错，如：javax.crypto.IllegalBlockSizeException: input must be under 256 bytes因此，基本上，您将密钥长度除以8 -11（如果有填充）。例如，如果您具有2048位密钥，则可以加密2048/8 = 256字节（如果有填充则为11字节）。因此，可以使用更大的密钥，也可以使用对称密钥加密数据，然后使用rsa加密该密钥（推荐的方法）参考：https://stackoverflow.com/questions/10007147/getting-a-illegalblocksizeexception-data-must-not-be-longer-than-256-bytes-when通过分段加密解决1.生成公钥私钥@Throws(Exception::class) fun genKeyPair(): Map<String?, String> { val keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM) keyPairGen.initialize(2048) val keyPair = keyPairGen.generateKeyPair() val publicKey = keyPair.public as RSAPublicKey val privateKey = keyPair.private as RSAPrivateKey val keyMap: MutableMap<String?, String> = HashMap(2) keyMap[PUBLIC_KEY] = Base64.encodeToString(publicKey.encoded, Base64.DEFAULT) keyMap[PRIVATE_KEY] = Base64.encodeToString(privateKey.encoded, Base64.DEFAULT) return keyMap }2.公钥加密 @Throws(Exception::class) fun encryptByPublicKey(data: ByteArray, publicKey: String?): ByteArray { val keyBytes: ByteArray = Base64.decode(publicKey, Base64.DEFAULT) val x509KeySpec = X509EncodedKeySpec(keyBytes) val keyFactory = KeyFactory.getInstance(KEY_ALGORITHM) val publicK: Key = keyFactory.generatePublic(x509KeySpec) // 对数据加密 val cipher = Cipher.getInstance(keyFactory.algorithm) cipher.init(Cipher.ENCRYPT_MODE, publicK) val inputLen = data.size val out = ByteArrayOutputStream() var offSet = 0 var cache: ByteArray var i = 0 // 对数据分段加密 while (inputLen - offSet > 0) { cache = if (inputLen - offSet > MAX_ENCRYPT_BLOCK) { cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK) } else { cipher.doFinal(data, offSet, inputLen - offSet) } out.write(cache, 0, cache.size) i++ offSet = i * MAX_ENCRYPT_BLOCK } val encryptedData = out.toByteArray() out.close() return encryptedData }3.私钥解密 @Throws(Exception::class) fun decryptByPrivateKey(encryptedData: ByteArray, privateKey: String?): ByteArray { val keyBytes: ByteArray = Base64.decode(privateKey, Base64.DEFAULT) val pkcs8KeySpec = PKCS8EncodedKeySpec(keyBytes) val keyFactory = KeyFactory.getInstance(KEY_ALGORITHM) val privateK: Key = keyFactory.generatePrivate(pkcs8KeySpec) val cipher = Cipher.getInstance(keyFactory.algorithm) cipher.init(Cipher.DECRYPT_MODE, privateK) val inputLen = encryptedData.size val out = ByteArrayOutputStream() var offSet = 0 var cache: ByteArray var i = 0 // 对数据分段解密 while (inputLen - offSet > 0) { cache = if (inputLen - offSet > MAX_DECRYPT_BLOCK) { cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK) } else { cipher.doFinal(encryptedData, offSet, inputLen - offSet) } out.write(cache, 0, cache.size) i++ offSet = i * MAX_DECRYPT_BLOCK } val decryptedData = out.toByteArray() out.close() return decryptedData }4.调用方法： val keyMap: Map<String?, String?> = RSACrypt.genKeyPair() val publicKey = keyMap[RSACrypt.PUBLIC_KEY] val privateKey = keyMap[RSACrypt.PRIVATE_KEY] val source = "身高一米七左右，标准的九头身，五官立体宛如艺术大师鬼斧神工之作，肌肤赛雪，宛如白玉般似能反射光彩。" + "“我和茹雪两情相悦，但对我们而言，你是第三者，所以请你自己主动退出，我愿意给你一笔钱，你开个价码吧！”啪，一声清脆的响声，干净利落地狠狠扇在韩斌的脸上。" + "乔智愿意当陶家的女婿，除了偿还父亲欠下的人情债之外，还有一个重要原因，陶茹雪本身出众，是琼金一枝花，知名度高，追求者众多。" val data = source.encodeToByteArray() val encodedData: ByteArray = RSACrypt.encryptByPublicKey(data, publicKey) Log.w("rsa", "加密后文字：${Base64.encodeToString(encodedData, Base64.DEFAULT)}") val decodedData: ByteArray = RSACrypt.decryptByPrivateKey(encodedData, privateKey) Log.w("rsa", "解密后文字: \r\n${String(decodedData)}")完整代码object RSACrypt { /** * 加密算法RSA */ const val KEY_ALGORITHM = "RSA" /** * 签名算法 */ const val SIGNATURE_ALGORITHM = "MD5withRSA" /** * 获取公钥的key */ const val PUBLIC_KEY = "RSAPublicKey" /** * 获取私钥的key */ const val PRIVATE_KEY = "RSAPrivateKey" /** * RSA最大加密明文大小 */ private const val MAX_ENCRYPT_BLOCK = 245 /** * RSA最大解密密文大小 */ private const val MAX_DECRYPT_BLOCK = 256 /** * 生成密钥对(公钥和私钥) * @return * @throws Exception */ @Throws(Exception::class) fun genKeyPair(): Map<String?, String> { val keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM) keyPairGen.initialize(2048) val keyPair = keyPairGen.generateKeyPair() val publicKey = keyPair.public as RSAPublicKey val privateKey = keyPair.private as RSAPrivateKey val keyMap: MutableMap<String?, String> = HashMap(2) keyMap[PUBLIC_KEY] = Base64.encodeToString(publicKey.encoded, Base64.DEFAULT) keyMap[PRIVATE_KEY] = Base64.encodeToString(privateKey.encoded, Base64.DEFAULT) return keyMap } /** * 私钥解密 * * @param encryptedData 已加密数据 * @param privateKey 私钥(BASE64编码) * @return * @throws Exception */ @Throws(Exception::class) fun decryptByPrivateKey(encryptedData: ByteArray, privateKey: String?): ByteArray { val keyBytes: ByteArray = Base64.decode(privateKey, Base64.DEFAULT) val pkcs8KeySpec = PKCS8EncodedKeySpec(keyBytes) val keyFactory = KeyFactory.getInstance(KEY_ALGORITHM) val privateK: Key = keyFactory.generatePrivate(pkcs8KeySpec) val cipher = Cipher.getInstance(keyFactory.algorithm) cipher.init(Cipher.DECRYPT_MODE, privateK) val inputLen = encryptedData.size val out = ByteArrayOutputStream() var offSet = 0 var cache: ByteArray var i = 0 // 对数据分段解密 while (inputLen - offSet > 0) { cache = if (inputLen - offSet > MAX_DECRYPT_BLOCK) { cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK) } else { cipher.doFinal(encryptedData, offSet, inputLen - offSet) } out.write(cache, 0, cache.size) i++ offSet = i * MAX_DECRYPT_BLOCK } val decryptedData = out.toByteArray() out.close() return decryptedData } /** * * 公钥加密 * * @param data 源数据 * @param publicKey 公钥(BASE64编码) * @return * @throws Exception */ @Throws(Exception::class) fun encryptByPublicKey(data: ByteArray, publicKey: String?): ByteArray { val keyBytes: ByteArray = Base64.decode(publicKey, Base64.DEFAULT) val x509KeySpec = X509EncodedKeySpec(keyBytes) val keyFactory = KeyFactory.getInstance(KEY_ALGORITHM) val publicK: Key = keyFactory.generatePublic(x509KeySpec) // 对数据加密 val cipher = Cipher.getInstance(keyFactory.algorithm) cipher.init(Cipher.ENCRYPT_MODE, publicK) val inputLen = data.size val out = ByteArrayOutputStream() var offSet = 0 var cache: ByteArray var i = 0 // 对数据分段加密 while (inputLen - offSet > 0) { cache = if (inputLen - offSet > MAX_ENCRYPT_BLOCK) { cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK) } else { cipher.doFinal(data, offSet, inputLen - offSet) } out.write(cache, 0, cache.size) i++ offSet = i * MAX_ENCRYPT_BLOCK } val encryptedData = out.toByteArray() out.close() return encryptedData } }

Android加密算法之RSA(一) RSA公钥加密私钥解密object RSACrypt { private const val transformation = "RSA/ECB/OAEPWithSHA-256AndMGF1Padding" /** * 公钥加密 * @param input 原文 * @param publicKey 公钥 */ fun encryptByPublicKey(input: ByteArray, publicKey: PublicKey): String { val cipher = Cipher.getInstance(transformation)//创建cipher对象 cipher.init(Cipher.ENCRYPT_MODE, publicKey)//初始化cipher对象 val encrypt = cipher.doFinal(input) //加密或解密 return Base64.encodeToString(encrypt, Base64.NO_WRAP) } /** * 私钥解密 * @param input 密文 * @param privateKey 私钥 */ fun decryptByPrivateKey(input: ByteArray, privateKey: PrivateKey): String { val cipher = Cipher.getInstance(transformation) //创建cipher对象 cipher.init(Cipher.DECRYPT_MODE, privateKey)//初始化cipher对象 val encrypt = cipher.doFinal(input)//加密或解密 return String(encrypt) } //生成RSAKey fun generateRSAKeyPair(keyLength: Int): KeyPair? { return try { val kpg = KeyPairGenerator.getInstance("RSA") kpg.initialize(keyLength) kpg.genKeyPair() } catch (e: NoSuchAlgorithmException) { e.printStackTrace() null } } }调用方法var keyPair = RSACrypt.generateRSAKeyPair(2048) keyPair?.let { val input = "123木头人" val encryptPublicKey = RSACrypt.encryptByPublicKey(input.encodeToByteArray(), it.public) val decryptPrivateKey = RSACrypt.decryptByPrivateKey(Base64.decode(encryptPublicKey, Base64.NO_WRAP), it.private) Log.w("rsa", "公钥加密 $encryptPublicKey") Log.w("rsa", "私钥解密 $decryptPrivateKey") }注意加密时如果内容过长会报：Caused by: javax.crypto.IllegalBlockSizeException: input must be under 256 bytes