【Kotlin】加密解密5：数字签名

数字签名

Api文档搜索Signature

RSACrypt封装一个返回privatekey和publickey的方法

  fun getPrivateKey():PrivateKey{
        //保存密钥对
        val privateKeyString = "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"
        //转成密钥对对象
        val kf = KeyFactory.getInstance("RSA")
        val privateKey:PrivateKey = kf.generatePrivate(PKCS8EncodedKeySpec(Base64.decode(privateKeyString)))
        return privateKey;
    }
    
    fun getPublicKey():PublicKey{
        //保存密钥对
        val publicKeyString = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAnBAaE7ji9zqSfhgarM9IKqpvL/1/EXELBSf6ku4G4wGwiFW9ItpMVKz0LTl/WuIx9HYkv/Z4ADjjUCxeKGwYrc8y3nxhnZhqg9DZn/Qt38lGmFEmVQXqnWIyDi02BCKU0z8yKAVnCk+670jZJrxEDqVnUq1YgAyp0GXEk/j8VRr/9L4NRXHzSvLXC+0gzL5oByHvJkus3XQRphFMJY9eBQ3FQAVv7F3P5pX0Qd+OTtO3C8XIP8g+5B5q/WcB8rVm/ZjVDzNkPNEGJfSp+wKkm8Gk3BEcd5AIlDEDKdQnkhitBpKEUoPRuANHvRu1KF2d/C1DIwFQSAyp/rdJB2d/VQIDAQAB"
        //转成密钥对对象
        val kf = KeyFactory.getInstance("RSA")
        val publicKey:PublicKey = kf.generatePublic(X509EncodedKeySpec(Base64.decode(publicKeyString)))
        return publicKey
    }

//数字签名
object SignatureDedmo {
    fun sign(input:String,privateKey:PrivateKey):String{
        //获取数字签名对象实例
        val signature = Signature.getInstance("SHA256withRSA")
        //初始化签名
        signature.initSign(privateKey)
        //设置数据源
        signature.update(input.toByteArray())
        //签名
        val sign = signature.sign()
        return Base64.encode(sign)
    }
    fun verify(input: String,publicKey:PublicKey,sign:String):Boolean{
        val signature = Signature.getInstance("SHA256withRSA")
        //初始化签名
        signature.initVerify(publicKey)
        //传入数据源
        signature.update(input.toByteArray())
        //校验签名信息
        val verify = signature.verify(Base64.decode(sign))
        return verify
    }
}

fun main(args:Array<String>){
    val privateKey = RSACrypt.getPrivateKey()
    val publicKey = RSACrypt.getPublicKey()
    val input = "name=iPhone&price=7888"
    val sign = SignatureDedmo.sign(input,privateKey)

    //******************** 校验 ********************

    println("校验："+SignatureDedmo.verify(input,publicKey,sign))
}

如果我们校验的时候把价格改为7

    println("校验："+SignatureDedmo.verify("name=iPhone&price=7",publicKey,sign))

数字签名流程

有一段文字，进行单项Hash函数（md5/sha1/sha256），假设我们用md5加密，生成了一串密文“011010111100”，对密文再次加密，这里用到了私钥，也就是RSA加密。加密完生成一串密文“xxxxxxxxxxxx”

到这里为止就是我们说的签名

当我们把明文和签名传给收件人，签名是一串乱乱的字符串，收件人用公钥对签名进行解密，解密出来的结果就是“011010111100”，也就是上面第一次对文字加密后的结果
收件人再对接收的明文进行一次MD5，如果结果不一致，说明被别人改了

收件人有我们的公钥因为进行了公钥互换

加密算法总结

到目前为止，加密算法就学完了