Add YubiKey PIV Ed25519 signing to README

- Add YubiKey signing feature to features list
- Document yubisigner-cli requirement and setup
- Add link to yubisigner project
- Update onion gateway address
- Note automatic signing with vim-yubisigner

1 files changed, 18 insertions, 3 deletions

diff --git a/README.md b/README.md
index f06b182..e796c1e 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,8 @@ Full write-up: [Posting to Usenet Anonymously with NeoMutt and Mail2News over To
 
 - Multi-account IMAP/SMTP (STARTTLS, port 143/587)
 - **Mail2news via Tor** — post to Usenet through a `.onion` SMTP gateway, no IP exposed
-- F9 macro → interactive post script (newsgroup, subject, editor, review, send)
+- **YubiKey PIV Ed25519 signatures** — automatic signing with hardware key (PGP-like clearsign format)
+- F7/F9 macro → interactive post script (newsgroup, subject, editor, review, send)
 - Ephemeral `.invalid` From address — not traceable, not replyable
 - No IMAP for the mail2news account — send-only
 
@@ -25,6 +26,7 @@ Full write-up: [Posting to Usenet Anonymously with NeoMutt and Mail2News over To
 | `torsocks` | Tor proxy wrapper             |
 | `swaks`    | SMTP test/send tool           |
 | `vim`      | Message editor                |
+| `yubisigner-cli` | YubiKey PIV signing (optional) |
 
 On Arch:
 ```bash
@@ -36,6 +38,17 @@ On Debian/Ubuntu:
 apt install neomutt tor torsocks swaks
 ```
 
+### YubiKey signing (optional)
+
+For automatic post signing with YubiKey PIV Ed25519:
+
+1. Install [yubisigner](https://github.com/Ch1ffr3punk/yubisigner) dependencies (Go, piv-go, etc.)
+2. Build `yubisigner-cli` wrapper (CLI version of yubisigner GUI)
+3. Configure YubiKey PIV slot 9c with Ed25519 key
+4. Install `vim-yubisigner` wrapper script
+
+The mail2news account is pre-configured to use `vim-yubisigner` as editor, which automatically signs messages with YubiKey after editing.
+
 ---
 
 ## Installation
@@ -73,8 +86,10 @@ Subject:      test post
 
 Write your message in the editor, review the draft, send.
 
-The post goes to `mail2news@xilb7y4kj6u6qfo45o3yk2kilfv54ffukzei3puonuqlncy7cn2afwyd.onion`,
-which forwards to Peanny NNTP and propagates from there.
+The post goes to `mail2news@qee4i7sags6phsvb2yodwecfj7noimfhhalsjktsvikrwotxzis3raad.onion`,
+which forwards to the NNTP server and propagates from there.
+
+**Posts are automatically signed** with YubiKey PIV Ed25519 in PGP-like clearsign format if `vim-yubisigner` is configured.
 
 ### Send directly from the shell (no NeoMutt)