Here’s ChatGPT o3’s take on the history of using public keys as user IDs.

Since the invention of public-key cryptography in the 1970s, several consumer-facing applications have used the user’s public key directly as their ID:

• PGP / GPG (1991) – Users share a short PGP fingerprint (a hash of their public key) as their email identity.

• Bitcoin addresses (2009) – A Base58-encoded hash of a public key acts as the account for sending/receiving funds.

• Bitmessage (2012) – The “BM-…” address is a Base58 public-key hash used for encrypted mail and broadcasts.

• Tox ID (2013) – The long Tox string embeds the full public key; add it to start an E2E-encrypted chat.

• Tor .onion v3 / Ricochet IM (2014) – A 56-character .onion address is derived from an Ed25519 public key and serves as the chat ID.

• Secure Scuttlebutt (2014) – Feed IDs look like @.ed25519; the key is the permanent identity.

• Ethereum-style addresses (2015) – 0x… hashes of public keys function as login/payment accounts across smart-contract chains.

• Nostr npub (2021) – An npub is a Bech32-encoded 32-byte public key; any client can verify signatures from it.