I seem to recall that the anonymity of car is based on obscuring transactions through bundling

Car? Autocorrect maybe?

I’m not XMR fanboy or expert, and it is some beautiful mathematics, but wayyyyyy over my head. That said, you might be referring to “ring signatures” that I guess you could say “bundles” the transactions together but that would be far too reductive, it’s way cooler and more complicated than that.

If I recall, there was talk of possible attack vectors, so they made it even more private. I’ll let wiki explain:

The transaction outputs, or notes, of users sending Monero are obfuscated through ring signatures, which groups a sender’s outputs with other decoy outputs.[14] Encryption of transaction amounts began in 2017 with the implementation of ring confidential transactions (RingCTs).[8][15] Developers also implemented a zero-knowledge proof method, “Bulletproofs”, which guarantee a transaction occurred without revealing its value.[16] Monero recipients are protected through “stealth addresses”, addresses generated by users to receive funds, but untraceable to an owner by a network observer.[8] These privacy features are enforced on the network by default.[8]

https://en.wikipedia.org/wiki/Monero#Privacy

So it looks like it was 2017 when they changed things. I know there was some discussion of switching from RingCTs to zk-SNARK (a form of “zero-knowledge proof”) which, in and of itself, is an amazing cryptographic concept. I implore you to check out the wiki on it if you have any interest in cryptography or mathematics I think it’s brilliant: https://en.wikipedia.org/wiki/Zero-knowledge_proof

So yeah, according to wiki, it seems as though they adopted zero-knowledge proofs… So not only ring signatures, but RingCTs (encrypted), plus ZKP, makes Monero pretty impenetrable. Which I think is cool af. As an engineer, I like seeing a typically abstract field/form of math be used in practical, real-world examples, as it doesn’t happen often.