Apparently, running "uuidgen" is too difficult for them. Which, shouldn't be a surprise for someone who already decided to use XOR "encryption".
Wouldn’t a random sequence using a seed as the secret be a better choice?
Yes. If you can build a cryptographically-secure random number generator, which can output a long stream of random bytes from a seed, congrats, you just invented a stream cipher. Just XOR your plaintext and random bytes, and you are good to go.
That's called a "stream cipher". ;-)
XOR encryption is unbreakable with an one-time pad that matches the message length (that's basically AES CTR). It's one of the most secure cryptography primitives we have.
The problem is deciding to use home-grown encryption.
This isn't a one-time pad. It's reused for every message.
It's reused every 8 bytes...
That too.
AES CTR isn't a one-time pad. It's as strong as AES, not theoretically unbreakable.
"Basically" is the key word there.
I usually say that encryption is the easy part. Just use XOR and you are good. All the complicated bits are related to key management.