CODEWITHSUNDEEP
node.jsencryption
Denis Alexeev
Denis Alexeev

Reputation: 105

How to set aes cfb feedback segment size in nodejs crypto lib?

I have this python 2.7 code with AES from Crypto.Cipher:

self.cipher_down = AES.new(key, AES.MODE_CFB, self.iv, segment_size=128)

How can I set cfb segment size (also known as feedback size) in node.js crypto lib? Here is my node.js snippet:

let cph = crypto.createCipheriv('aes-256-cfb', this.key, this.iv);

Upvotes: 2

Views: 497

Answers (1)

Topaco
Topaco

Reputation: 49351

The crypto module of NodeJS is based on OpenSSL and therefore uses the same names, see here. Whether a mode is supported in NodeJS depends therefore also on OpenSSL, see here.

OpenSSL and thus NodeJS append the number of bits n encrypted per encryption step to the name, i.e. ...-cfbn (e.g. aes-128-cfb8). ...-cfb8 therefore corresponds to segment_size = 8, with the exception of n = 128 or segment_size = 128, which is simply referred to as ...-cfb.

Since in Python n must be a multiple of 8 (at least for PyCryptodome) there is no counterpart to ...-cfb1.

There is a bug in the legacy PyCrypto library in the context of CFB mode that requires the plaintext to have a length that is an integer multiple of the segment length. Otherwise the following error occurs: Input strings must be a multiple of the segment size 16 in length.

Upvotes: 2

Related Questions