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POIssues in RSA encryption in Java class
 

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  1. POIssues in RSA encryption in Java class
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    <pre><code>public class MyEncrypt { public void saveToFile(String fileName, BigInteger mod, BigInteger exp) throws IOException { ObjectOutputStream oout = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(fileName))); try { oout.writeObject(mod); oout.writeObject(exp); } catch (Exception e) { throw new IOException("Unexpected error", e); } finally { oout.close(); } } public static void main(String[] args) throws Exception { MyEncrypt myEncrypt = new MyEncrypt(); KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA"); kpg.initialize(128); KeyPair kp = kpg.genKeyPair(); RSAPublicKey publicKey = (RSAPublicKey) kp.getPublic(); RSAPrivateKey privateKey = (RSAPrivateKey) kp.getPrivate(); KeyFactory fact = KeyFactory.getInstance("RSA"); RSAPublicKeySpec pub = fact.getKeySpec(kp.getPublic(), RSAPublicKeySpec.class); RSAPrivateKeySpec priv = fact.getKeySpec(kp.getPrivate(), RSAPrivateKeySpec.class); myEncrypt.saveToFile("public.key", pub.getModulus(), pub.getPublicExponent()); myEncrypt.saveToFile("private.key", priv.getModulus(), priv.getPrivateExponent()); String encString = myEncrypt.bytes2String(myEncrypt.rsaEncrypt("pritesh".getBytes())); System.out.println("encrypted : " + encString); String decString = myEncrypt.bytes2String(myEncrypt.rsaDecrypt(encString.getBytes())); System.out.println("decrypted : " + decString); } PublicKey readKeyFromFile(String keyFileName) throws Exception { InputStream in = new FileInputStream(keyFileName); ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(in)); try { BigInteger m = (BigInteger) oin.readObject(); BigInteger e = (BigInteger) oin.readObject(); RSAPublicKeySpec keySpec = new RSAPublicKeySpec(m, e); KeyFactory fact = KeyFactory.getInstance("RSA"); PublicKey pubKey = fact.generatePublic(keySpec); return pubKey; } catch (Exception e) { throw new RuntimeException("Spurious serialisation error", e); } finally { oin.close(); } } PrivateKey readPrivateKeyFromFile(String keyFileName) throws Exception { InputStream in = new FileInputStream(keyFileName); ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(in)); try { BigInteger m = (BigInteger) oin.readObject(); BigInteger e = (BigInteger) oin.readObject(); RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m, e); KeyFactory fact = KeyFactory.getInstance("RSA"); PrivateKey pubKey = fact.generatePrivate(keySpec); return pubKey; } catch (Exception e) { throw new RuntimeException("Spurious serialisation error", e); } finally { oin.close(); } } public byte[] rsaEncrypt(byte[] data) throws Exception { byte[] src = new byte[] { (byte) 0xbe, (byte) 0xef }; PublicKey pubKey = this.readKeyFromFile("public.key"); Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, pubKey); byte[] cipherData = cipher.doFinal(data); return cipherData; } public byte[] rsaDecrypt(byte[] data) throws Exception { byte[] src = new byte[] { (byte) 0xbe, (byte) 0xef }; PrivateKey pubKey = this.readPrivateKeyFromFile("private.key"); Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.DECRYPT_MODE, pubKey); byte[] cipherData = cipher.doFinal(data); return cipherData; } private String bytes2String(byte[] bytes) { StringBuilder string = new StringBuilder(); for (byte b: bytes) { String hexString = Integer.toHexString(0x00FF &amp; b); string.append(hexString.length() == 1 ? "0" + hexString : hexString); } return string.toString(); } } </code></pre> <p>I am getting this error:</p> <pre><code>Exception in thread "main" java.security.InvalidParameterException: RSA keys must be at least 512 bits long at sun.security.rsa.RSAKeyPairGenerator.initialize(RSAKeyPairGenerator.java:70) at java.security.KeyPairGenerator$Delegate.initialize(KeyPairGenerator.java:631) at java.security.KeyPairGenerator.initialize(KeyPairGenerator.java:340) at MyEncrypt.main(MyEncrypt.java:42) </code></pre> <p>I have make this class from <a href="http://www.javamex.com/tutorials/cryptography/rsa_encryption_2.shtml" rel="nofollow">http://www.javamex.com/tutorials/cryptography/rsa_encryption_2.shtml</a> example</p> <hr> <p><code> </p> <p>public class MyEncrypt {</p> <pre><code>static final String HEXES = "0123456789ABCDEF"; byte[] buf = new byte[1024]; public void saveToFile(String fileName, BigInteger mod, BigInteger exp) throws IOException { ObjectOutputStream oout = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(fileName))); try { oout.writeObject(mod); oout.writeObject(exp); } catch (Exception e) { throw new IOException("Unexpected error", e); } finally { oout.close(); } } public static void main(String[] args) throws Exception { MyEncrypt myEncrypt = new MyEncrypt(); KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA"); kpg.initialize(2048); KeyPair kp = kpg.genKeyPair(); RSAPublicKey publicKey = (RSAPublicKey) kp.getPublic(); RSAPrivateKey privateKey = (RSAPrivateKey) kp.getPrivate(); KeyFactory fact = KeyFactory.getInstance("RSA"); RSAPublicKeySpec pub = fact.getKeySpec(kp.getPublic(), RSAPublicKeySpec.class); RSAPrivateKeySpec priv = fact.getKeySpec(kp.getPrivate(), RSAPrivateKeySpec.class); myEncrypt.saveToFile("public.key", pub.getModulus(), pub.getPublicExponent()); myEncrypt.saveToFile("private.key", priv.getModulus(), priv.getPrivateExponent()); String encString = myEncrypt.rsaEncrypt("pritesh"); System.out.println("encrypted : " + encString); String decString = myEncrypt.rsaDecrypt(encString); System.out.println("decrypted : " + decString); String main_file_path = "resume.doc"; String main_encrypt_file_path = "encrypt.doc"; String main_decrypt_file_path = "decrypt.doc"; myEncrypt.rsaEncrypt(new FileInputStream(main_file_path),new FileOutputStream(main_encrypt_file_path)); // Decrypt myEncrypt.rsaDecrypt(new FileInputStream(main_encrypt_file_path),new FileOutputStream(main_decrypt_file_path)); } PublicKey readKeyFromFile(String keyFileName) throws Exception { InputStream in = new FileInputStream(keyFileName); ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(in)); try { BigInteger m = (BigInteger) oin.readObject(); BigInteger e = (BigInteger) oin.readObject(); RSAPublicKeySpec keySpec = new RSAPublicKeySpec(m, e); KeyFactory fact = KeyFactory.getInstance("RSA"); PublicKey pubKey = fact.generatePublic(keySpec); return pubKey; } catch (Exception e) { throw new RuntimeException("Spurious serialisation error", e); } finally { oin.close(); } } PrivateKey readPrivateKeyFromFile(String keyFileName) throws Exception { InputStream in = new FileInputStream(keyFileName); ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(in)); try { BigInteger m = (BigInteger) oin.readObject(); BigInteger e = (BigInteger) oin.readObject(); RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m, e); KeyFactory fact = KeyFactory.getInstance("RSA"); PrivateKey pubKey = fact.generatePrivate(keySpec); return pubKey; } catch (Exception e) { throw new RuntimeException("Spurious serialisation error", e); } finally { oin.close(); } } public String rsaEncrypt(String plaintext) throws Exception { PublicKey pubKey = this.readKeyFromFile("public.key"); Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, pubKey); byte[] ciphertext = cipher.doFinal(plaintext.getBytes("UTF-8")); return this.byteToHex(ciphertext); } public void rsaEncrypt(InputStream in, OutputStream out) throws Exception { try { PublicKey pubKey = this.readKeyFromFile("public.key"); Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, pubKey); // Bytes written to out will be encrypted out = new CipherOutputStream(out, cipher); // Read in the cleartext bytes and write to out to encrypt int numRead = 0; while ((numRead = in.read(buf)) &gt;= 0){ out.write(buf, 0, numRead); } out.close(); } catch (java.io.IOException e){ e.printStackTrace(); } } public void rsaDecrypt(InputStream in, OutputStream out) throws Exception { try { PrivateKey pubKey = this.readPrivateKeyFromFile("private.key"); Cipher dcipher = Cipher.getInstance("RSA"); dcipher.init(Cipher.DECRYPT_MODE, pubKey); // Bytes read from in will be decrypted in = new CipherInputStream(in, dcipher); // Read in the decrypted bytes and write the cleartext to out int numRead = 0; while ((numRead = in.read(buf)) &gt;= 0) { out.write(buf, 0, numRead); } out.close(); } catch (java.io.IOException e) { e.printStackTrace(); } } public String rsaDecrypt(String hexCipherText) throws Exception { PrivateKey pubKey = this.readPrivateKeyFromFile("private.key"); Cipher cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.DECRYPT_MODE, pubKey); String plaintext = new String(cipher.doFinal(this.hexToByte(hexCipherText)), "UTF-8"); return plaintext; } public static String byteToHex( byte [] raw ) { if ( raw == null ) { return null; } final StringBuilder hex = new StringBuilder( 2 * raw.length ); for ( final byte b : raw ) { hex.append(HEXES.charAt((b &amp; 0xF0) &gt;&gt; 4)) .append(HEXES.charAt((b &amp; 0x0F))); } return hex.toString(); } public static byte[] hexToByte( String hexString){ int len = hexString.length(); byte[] ba = new byte[len / 2]; for (int i = 0; i &lt; len; i += 2) { ba[i/2] = (byte) ((Character.digit(hexString.charAt(i), 16) &lt;&lt; 4) + Character.digit(hexString.charAt(i+1), 16)); } return ba; } </code></pre> <p>} </code></p> <p>It works well with text file but giving issue on files like docx and video any idea?</p>
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