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POEncrypting with RSA private key in Java
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copied!<p>I'm trying to encrypt some content with an RSA private key. </p> <p>I'm following this example: <a href="http://www.junkheap.net/content/public_key_encryption_java" rel="nofollow noreferrer">http://www.junkheap.net/content/public_key_encryption_java</a><br> <br> but converting it to use private keys rather than public. Following that example, I think what I need to do is:</p> <ul><li>Read in a DER-format private key</li> <li>Generate a PCKS8EncodedKeySpec</li> <li>call generatePrivate() from KeyFactory to get a private key object</li> <li>Use that private key object with the Cipher object to do the encryption</li> </ul> <p>So, the steps:</p> <p>The key was generated from openssl with:</p> <p><code>openssl genrsa -aes256 -out private.pem 2048</code></p> <p>and then was converted to DER format with:</p> <p><code>openssl rsa -in private.pem -outform DER -out private.der</code></p> <p>I generate the PKCS8EncodedKeySpec with:</p> <pre><code>byte[] encodedKey = new byte[(int)inputKeyFile.length()]; try { new FileInputStream(inputKeyFile).read(encodedKey); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } PKCS8EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(encodedKey); return privateKeySpec; </code></pre> <p>And then generate the private key object with:</p> <pre><code>PrivateKey pk = null; try { KeyFactory kf = KeyFactory.getInstance(RSA_METHOD); pk = kf.generatePrivate(privateKeySpec); } catch (NoSuchAlgorithmException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvalidKeySpecException e) { // TODO Auto-generated catch block e.printStackTrace(); } return pk; </code></pre> <p>However, on the call to:</p> <pre><code>pk = kf.generatePrivate(privateKeySpec); </code></pre> <p>I get:</p> <pre><code>java.security.spec.InvalidKeySpecException: Unknown key spec. at com.sun.net.ssl.internal.ssl.JS_KeyFactory.engineGeneratePrivate(DashoA12275) at com.sun.net.ssl.internal.ssl.JSA_RSAKeyFactory.engineGeneratePrivate(DashoA12275) at java.security.KeyFactory.generatePrivate(KeyFactory.java:237) </code></pre> <p>Questions:</p> <ul> <li>Is the general approach right?</li> <li>Is the PCKS8EncodedKeySpec the right keyspec to use?</li> <li>Any thoughts on the invalid key spec error?</li> </ul>

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