Cracking Stream Cipher I need to crack a stream cipher. I have a set of plain text and encrypted text pairs.

The hint to the question asks me to use entropy analysis and look at the hex dump of the encrypted text. However, I couldn't find anything useful in either of them.

What should be the approach to solve this cipher?
If the key is always the same and there is no IV (or fixed IV), then

$$plaintext1 \oplus ciphertext1 \oplus ciphertext2 = plaintext2$$