Need solution for wrong IV length in AES

user_849550 0
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I'm trying to implement AES in Java and this is the code I use:

 byte[] sessionKey = {00000000000000000000000000000000};
 byte[] iv = {00000000000000000000000000000000};
 byte[] plaintext = "6a84867cd77e12ad07ea1be895c53fa3".getBytes();
 Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

 cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(sessionKey, "AES"), new IvParameterSpec(iv));
 byte[] ciphertext = cipher.doFinal(plaintext);

 cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(sessionKey, "AES"), new IvParameterSpec(iv));
 byte[] deciphertext = cipher.doFinal(ciphertext);

I need this fixed key and IV for test purpose but I get the following exception:

Exception in thread "main"
java.security.InvalidAlgorithmParameterException: 
  Wrong IV length: must be 16 bytes long    at
com.sun.crypto.provider.SunJCE_h.a(DashoA12275)     at
com.sun.crypto.provider.AESCipher.engineInit(DashoA12275)   at
javax.crypto.Cipher.a(DashoA12275)  at
javax.crypto.Cipher.a(DashoA12275)  at
javax.crypto.Cipher.init(DashoA12275)   at
javax.crypto.Cipher.init(DashoA12275)

How can I use this fixed IV with this implementation of AES? Is there any way?

initialization-vector aes java
6 Answers

The reason why I had this problem was because I was reading the IV as a String, and converting it to a byte array the wrong way.

Right way:

Hex.decodeHex(initializationVector.toCharArray()

using org.apache.commons.codec.binary.Hex

Wrong way:

initializationVector.getBytes()

The reason this was wrong, is because when you call getBytes(), it just takes all bits that represent the string and cuts them into bytes. So 0 ends up being written as the bits that make up the index of 0 in the Unicode table, which is not 0 but 30, and which would be written on 2 bytes.

Conversely, what you want here is actually that 0 be represented as the byte 00000000.

user_28735070

Not related to this but faced same issue.

IvParameterSpec ivParameterSpec = new IvParameterSpec(key1.getBytes("UTF-8")); SecretKeySpec skeySpec = new SecretKeySpec(key2.getBytes("UTF-8"),"AES"); The mistake I made was key1 and key2 were Strings of length greater than 16. Changing their length to 16 fixed it.

user_129321110
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