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    <p>Since you're generating the encryption keys every time, the program won't be able to decrypt a ciphertext that was created using a different encryption key. You'll need to find a way to persist the encryption key if you want to reuse it between runs of your program.</p> <p>The following program is a smaller version of your original example except that it encrypts and decrypts the plaintext with each cipher. I didn't have access to the <code>StringEncrypter</code> class so I wrote a simple version:</p> <pre><code>import javax.crypto.Cipher; import javax.crypto.KeyGenerator; import javax.crypto.SecretKey; public class EncTest { public static void main(String[] args) throws Exception { System.out.println("Testing method using secret key"); String plaintext = "hello world"; SecretKey aesKlic = KeyGenerator.getInstance("AES").generateKey(); SecretKey desKlic = KeyGenerator.getInstance("DES").generateKey(); SecretKey desedeKlic = KeyGenerator.getInstance("DESede").generateKey(); SecretKey rc2Klic = KeyGenerator.getInstance("RC2").generateKey(); SecretKey blowfishKlic = KeyGenerator.getInstance("Blowfish").generateKey(); StringEncrypter[] ciphers = new StringEncrypter[] { new StringEncrypter(aesKlic, aesKlic.getAlgorithm()), new StringEncrypter(desKlic, desKlic.getAlgorithm()), new StringEncrypter(desedeKlic, desedeKlic.getAlgorithm()), new StringEncrypter(rc2Klic, rc2Klic.getAlgorithm()), new StringEncrypter(blowfishKlic, blowfishKlic.getAlgorithm()) }; byte[][] ciphertexts = new byte[ciphers.length][]; int i = 0; for (StringEncrypter cipher : ciphers) { ciphertexts[i] = cipher.encrypt(plaintext); System.out.println(cipher.getAlgorithm() + " encrypted: " + hexEncode(ciphertexts[i])); i++; } System.out.println(); i = 0; for (StringEncrypter cipher : ciphers) { System.out.println(cipher.getAlgorithm() + " decrypted: " + cipher.decrypt(ciphertexts[i])); i++; } } // Hex encoding lifted from commons-codec private static String hexEncode(byte [] input) { return new String(encodeHex(input)); } private static char[] encodeHex(byte[] data) { int l = data.length; char[] out = new char[l &lt;&lt; 1]; // two characters form the hex value. for (int i = 0, j = 0; i &lt; l; i++) { out[j++] = DIGITS[(0xF0 &amp; data[i]) &gt;&gt;&gt; 4 ]; out[j++] = DIGITS[ 0x0F &amp; data[i] ]; } return out; } private static final char[] DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; private static class StringEncrypter { private final SecretKey key; private final String algorithm; public StringEncrypter(SecretKey key, String algorithm) { this.key = key; this.algorithm = algorithm; } public String getAlgorithm() { return algorithm; } public byte[] encrypt(String input) throws Exception { Cipher cipher = Cipher.getInstance(algorithm); cipher.init(Cipher.ENCRYPT_MODE, key); return cipher.doFinal(input.getBytes("UTF-8")); } public String decrypt(byte[] input) throws Exception { Cipher cipher = Cipher.getInstance(algorithm); cipher.init(Cipher.DECRYPT_MODE, key); return new String(cipher.doFinal(input)); } } } </code></pre>
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    1. POCannot decrypt cyphertext from text file, symmetric key implement. in java
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    1. COThanks for answer. I just didn't realize that I got always new key :) But when I print out the key, I get something like this "javax.crypto.spec.SecretKeySpec@1708d;" and probably cant use it. I really need to be able store/restore the key but dont know how. I have some ideas but it would look propably bad. Could you provide some example please ?
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    2. COYou can get the raw key material using SecretKey#getEncoded(). You could then hex/base64 encode this and store it somewhere. However, this is quite insecure if you don't have a way to properly store your key material. I'd recommend using an appropriate PBE cipher instead
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