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我正在用 Java 实现一个 WebService，其中服务器需要使用 RSA 算法向客户端发送一个 3DES 密钥。对称是由服务器生成的。服务器和客户端都有自己的 RSA 密钥对，之前交换过。

在此代码中，服务器将对称密钥发送给客户端。

@WebMethod
public byte[] getSymmetricKey(){
    try{
        Cipher cipher = Cipher.getInstance("RSA");

        // First, encrypts the symmetric key with the client's public key
        cipher.init(Cipher.ENCRYPT_MODE, this.clientKey);
        byte[] partialCipher = cipher.doFinal(this.key.getBytes());

        // Finally, encrypts the previous result with the server's private key
        cipher.init(Cipher.ENCRYPT_MODE, this.privateKey);
        byte[] cipherData = cipher.doFinal(partialCipher);

        return cipherData;
    }catch (Exception ex){
        ex.printStackTrace();
    }

}

当我使用服务器的私钥运行加密时，出现IllegalBlockSizeException. 如果默认激活填充，为什么会出现此异常？我也尝试过使用 . 显式激活填充Cipher.getInstance("RSA/ECB/PKCS1Padding")。最后，这是异常输出：

    SEVERE: javax.crypto.IllegalBlockSizeException: Data must not be longer than 245 bytes
javax.crypto.IllegalBlockSizeException: Data must not be longer than 245 bytes
    at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:346)
    at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:391)
    at javax.crypto.Cipher.doFinal(Cipher.java:2087)
    at server.FileTransfererImpl.getSymmetricKey(FileTransfererImpl.java:112)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.reflect.misc.Trampoline.invoke(Unknown Source)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.sun.xml.internal.ws.api.server.MethodUtil.invoke(Unknown Source)
    at com.sun.xml.internal.ws.api.server.InstanceResolver$1.invoke(Unknown Source)
    at com.sun.xml.internal.ws.server.InvokerTube$2.invoke(Unknown Source)
    at com.sun.xml.internal.ws.server.sei.EndpointMethodHandler.invoke(Unknown Source)
    at com.sun.xml.internal.ws.server.sei.SEIInvokerTube.processRequest(Unknown Source)
    at com.sun.xml.internal.ws.api.pipe.Fiber.__doRun(Unknown Source)
    at com.sun.xml.internal.ws.api.pipe.Fiber._doRun(Unknown Source)
    at com.sun.xml.internal.ws.api.pipe.Fiber.doRun(Unknown Source)
    at com.sun.xml.internal.ws.api.pipe.Fiber.runSync(Unknown Source)
    at com.sun.xml.internal.ws.server.WSEndpointImpl$2.process(Unknown Source)
    at com.sun.xml.internal.ws.transport.http.HttpAdapter$HttpToolkit.handle(Unknown Source)
    at com.sun.xml.internal.ws.transport.http.HttpAdapter.handle(Unknown Source)
    at com.sun.xml.internal.ws.transport.http.server.WSHttpHandler.handleExchange(Unknown Source)
    at com.sun.xml.internal.ws.transport.http.server.WSHttpHandler.handle(Unknown Source)
    at com.sun.net.httpserver.Filter$Chain.doFilter(Unknown Source)
    at sun.net.httpserver.AuthFilter.doFilter(Unknown Source)
    at com.sun.net.httpserver.Filter$Chain.doFilter(Unknown Source)
    at sun.net.httpserver.ServerImpl$Exchange$LinkHandler.handle(Unknown Source)
    at com.sun.net.httpserver.Filter$Chain.doFilter(Unknown Source)
    at sun.net.httpserver.ServerImpl$Exchange.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
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1 回答 1

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我今天正在研究一些东西，发现了这个问题。由于尚未得到答复，我将把它留在这里以供将来参考。

根据 PKCS #1，该RSAES-PKCS1-V1_5-ENCRYPT算法最多可以加密k - 11字节，其中k密钥的“大小”以字节为单位。这 11 个字节用于“标题”。

如果您使用的是 2048 位 RSA 密钥，那么k = 256您可以加密最多256 - 11 = 245字节的数据。

检查实际大小this.key。

于 2016-09-21T22:49:07.547 回答