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POjavax.crypto.BadPaddingException: Data must start with zero” exception. Why does it occur?
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copied!<blockquote> <p><strong>Possible Duplicate:</strong><br> <a href="https://stackoverflow.com/questions/6483181/javax-crypto-badpaddingexception-data-must-start-with-zero-exception">“javax.crypto.BadPaddingException: Data must start with zero” exception.</a> </p> </blockquote> <p>I am trying to separate the usage of the encrypt and decrypt methods into two different classes. However, I encountered the abovementioned exception while I was decrypting a string.</p> <p>Below is my code:</p> <pre><code>import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import javax.crypto.Cipher; public class EncryptAndDecrypt { /** * */ public static Cipher createCipher () throws Exception{ Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); return cipher; } public static KeyPair generateKey () throws NoSuchAlgorithmException{ KeyPairGenerator keyGen = KeyPairGenerator.getInstance ("RSA"); keyGen.initialize(1024); KeyPair key = keyGen.generateKeyPair(); return key; } public static byte [] encrypt (String str, Cipher cip, KeyPair key) { byte [] cipherText = null; try { byte [] plainText = str.getBytes("UTF8"); cip.init(Cipher.ENCRYPT_MODE, key.getPublic()); cipherText = cip.doFinal(plainText); } catch (Exception e) { e.printStackTrace(); } return cipherText; } public static String decrypt (byte [] c, Cipher cip, KeyPair key) throws Exception { cip.init(Cipher.DECRYPT_MODE, key.getPrivate()); byte [] decryptedPlainText = cip.doFinal (c);// exception occurred here String decryptedPlainStr = new String (decryptedPlainText, "UTF8"); return decryptedPlainStr; } } // A separate class that uses the encrypt method in EncryptAndDecrypt public class EncryptionApp { public static void main (String [] args) { System.out.println (getEncrypted()); } public static byte [] getEncrypted () { byte [] encyptedByte = null; try { String plainText = "hello"; Cipher cip = EncryptAndDecrypt.createCipher(); KeyPair key = EncryptAndDecrypt.generateKey(); encyptedByte = EncryptAndDecrypt.encrypt(plainText, cip, key); String str = new String (encyptedByte, "UTF8"); System.out.println (str); } catch (Exception e) { e.printStackTrace(); } return encyptedByte; } } public class DecryptedApp { /** * A separate class to use the decrypt method in EncryptAndDecrypt */ public static void main(String[] args) { System.out.println (useDecrypted ()); } public static String useDecrypted () { String decryptedText = null; try { Cipher cip = EncryptAndDecrypt.createCipher(); KeyPair key = EncryptAndDecrypt.generateKey(); byte [] encrypted = EncryptionApp.getEncrypted(); System.out.println (encrypted); decryptedText = EncryptAndDecrypt.decrypt(encrypted, cip, key) ; } catch (Exception e) { e.printStackTrace(); } return decryptedText; } </code></pre> <p>}</p>

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