CODEWITHSUNDEEP
encryptioncryptographycbc-modeinitialization-vector
Shehzaan
Shehzaan

Reputation: 69

Is there any way to run aes-128-cbc encryption in openssl without iv?

I am trying to encrypt a text file with opensslusing aes-128-cbc encryption and I was wondering if there was a way I could encrypt it only using the key and not the iv?

Everytime I try to run: 

openssl enc -aes-128-cbc -e -in dummy_file.txt -out dummy.aes-128-cbc.bin -K 00112233445566778889aabbccddeeff

I get the error saying iv undefined and the encrypted file it generates is empty and it is not even a binary file.

Upvotes: 3

Views: 9745

Answers (1)

Maarten Bodewes
Maarten Bodewes

Reputation: 94078

No, that's not possible, CBC requires an IV. You can however set the IV to all zeros. As the IV is XOR'ed with the first block of plaintext before encryption, this comes down to having no IV at all: you would directly encrypt the first block of plaintext with the block cipher.

Note that creating multiple ciphertext with the same key and IV will not result in a secure cipher. For CBC it is required to have a random (or at least unpredictable) IV. Otherwise an attacker can at least see which plaintext start with identical blocks of data.

The IV always consists of 16 bytes for AES, which comes down to 32 hexadecimal zeros, of course for the -iv command line parameter of openssl.

Upvotes: 10

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