encryption - Java Encrypt a file using aes256/ CBC/PKCS7Padding -

i'm trying encrypt file using aes256- cbc-pkcs7padding . i'm using bouncy castle library , exception

java.lang.illegalargumentexception: invalid parameter passed aes init - org.bouncycastle.crypto.params.parameterswithiv @ org.bouncycastle.crypto.engines.aesengine.init(unknown source) @ org.bouncycastle.crypto.paddings.paddedbufferedblockcipher.init(unknown source) 

here source code :

public class crypto {      public static final int aes_key_size = 256;     public static int blocksize = 16;     private final blockcipher aescipher = new aesengine();     private paddedbufferedblockcipher cipher = new paddedbufferedblockcipher(aescipher, new pkcs7padding());     private byte[] iv;     private keyparameter key;      public crypto() throws nosuchalgorithmexception {         keygenerator kg = keygenerator.getinstance("aes");         kg.init(aes_key_size);         secretkey sk = kg.generatekey();         key = new keyparameter(sk.getencoded());       }     public void cryptozip(file plikzip, file plikaes) throws ioexception, datalengthexception, illegalstateexception, invalidciphertextexception {          byte[] input = files.readallbytes(plikzip.topath());         byte[] cryptout = encrypt(input);         fileoutputstream fos = new fileoutputstream(plikaes);         fos.write(cryptout);         fos.close();        }       private byte[] encrypt(byte[] input) throws datalengthexception, illegalstateexception, invalidciphertextexception {            iv = new byte[blocksize];         securerandom random = new securerandom();         random.nextbytes(iv);          cipher.init(true, new parameterswithiv(key, iv)); // problem here           byte[] output = new byte[cipher.getoutputsize(input.length)];         int byteswrittenout = cipher.processbytes(             input, 0, input.length, output, 0);          cipher.dofinal(output, byteswrittenout);          return output;      } } 

any suggestion how fix , explanation i'm doing wrong helpful.

what you're missing indication of mode. if missing ecb mode assumed, , ecb mode doesn't take iv. paddedbufferedblockcipher buffering, ecb mode. init mode passes parameters aesengine, , aesengine rejects iv accepts keys.

in code, following direct fix problem:

private final cbcblockcipher aesciphercbc = new cbcblockcipher(aescipher); private final paddedbufferedblockcipher cipher = new paddedbufferedblockcipher(aesciphercbc, new pkcs7padding()); 

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i'll include following rewrite show different way of writing down. note didn't touch upon handling iv or exceptions correctly. obviously, large files, may want stream contents and/or map files.

// renamed crypto horrible name public class fileencryptor {      // lets use uppercase constant names     public static final int aes_key_size = 256;      // field needed, rest can generated on fly     private final keyparameter key;      public fileencryptor() throws nosuchalgorithmexception {         key = generatekey();     }      private static keyparameter generatekey() {         // removed keygenerator that's dependent on jca crypto-api          securerandom keyrng = new securerandom();         byte[] keydata = new byte[aes_key_size / byte.size];         keyrng.nextbytes(keydata);         return new keyparameter(keydata);     }      // code doesn't zip itself, no need include in method name     public void encryptfile(file plaintextfile, file ciphertextfile) throws ioexception, datalengthexception, illegalstateexception, invalidciphertextexception {         byte[] plaintext = files.readallbytes(plaintextfile.topath());         byte[] ciphertext = encrypt(plaintext);         // try , symmetric, use files functionality reading *and writing*         files.write(ciphertextfile.topath(), ciphertext);     }       private byte[] encrypt(byte[] plaintext) throws datalengthexception, illegalstateexception, invalidciphertextexception {         // create cipher         final blockcipher aes = new aesfastengine();         cbcblockcipher aescbc = new cbcblockcipher(aes);         paddedbufferedblockcipher aescbcpadded =                 new paddedbufferedblockcipher(aescbc, new pkcs7padding());          // create iv         byte[] iv = new byte[aes.getblocksize()];         securerandom random = new securerandom();         random.nextbytes(iv);          // initialize cipher iv         parameterswithiv paramswithiv = new parameterswithiv(key, iv);         aescbcpadded.init(true, paramswithiv); // problem here          // encrypt         byte[] ciphertext = new byte[aescbcpadded.getoutputsize(plaintext.length)];         int byteswrittenout = aescbcpadded.processbytes(             plaintext, 0, plaintext.length, ciphertext, 0);         aescbcpadded.dofinal(ciphertext, byteswrittenout);          // that's great, iv now? need include in returned ciphertext!         return ciphertext;     } }