Why asymmetric cryptography exists

1. No pre-shared secret — strangers on the Internet can still establish trust (TLS certificates, Signal, SSH).
2. Signatures — prove authorship and integrity without revealing the private key.
3. Scale — N users need N keypairs, not N² pairwise passwords.
4. Forward design for money — Bitcoin addresses commit to public keys (or hashes thereof); spending requires a signature only the private key can make.

Without asymmetric crypto, every courier would need a unique shared Ring with every correspondent — logistics fit for Sauron, not for the free peoples of the Net.