Here's one for Monero which I won't do it the injustice of calling it "broken", simply a "vulnerability"....
.....if Darkcoin's algo ever gets "hacked", i.e. if a successful trace back to a sender of an anonymised transaction occurs, then only that one transaction is affected. The rest of the entire blockchain history is still safe.
On the other hand, if a solution is ever found for cryptonote encryption algorithm then the ENTIRE BLOCKCHAIN can be sprung with that one can opener. Cryptonote is therefore a timebomb. Your transaction might be anonymous today but not in 5 years time.
Be careful what you refer to as "architecturally broken".
If the cryptography behind ring signatures are cracked then everything using Schnorr signatures or EdDSA is in trouble. The same cryptography that protects Monero (
Ed25519) is used by: OpenSSH, I2P, GnuPG, Google End-To-End, Core Secret for iOS, and mcrypt.
So yes, if Ed25519 is broken then Monero would have to rely on stealth addresses for protection. But hey, in that event all the masternodes could be accessed, as OpenSSH would be broken too:)
Except that everything you thought was anonymous in Monero up until that point all of a sudden is not anymore.
And if you anonymized your coins with Darkcoin before "all the masternodes are accessed", you're still safe transacting anonymously. And all your previous transactions are still private as well.