doc/TorMessenger/SASL.md

+SASL ECDSA-NIST256P-CHALLENGE support was added in Tor Messenger starting with version 0.3.0b1. To generate a key pair, follow the following steps:
+
+Paste the following code snippet in the Firefox (or Tor Browser) web console to generate a private key (logged as a hex string). This step will also generate the IRC command to execute to set the public key on the server (starting with `/msg nickserv set`)
+
+1. Start Firefox (or Tor Browser) and open the web console.
+1. Paste the following code:
+
+{{{
+crypto.subtle.generateKey({ name: "ECDSA", namedCurve: "P-256" }, true, ["sign"])
+.then((kp) => {
+  let padStart = (s, l, c) => Array(l - s.length + 1).join(c || " ") + s;
+  let padEnd = (s, l, c) => s + Array(l - s.length + 1).join(c || " ");
+  crypto.subtle.exportKey("jwk", kp.privateKey).then((o) => {
+    // convert from base64url to hex string
+    let d = o.d;
+    let padLen = (4 - (d.length % 4)) % 4;
+    d = padEnd(d, d.length + padLen, "=")
+         .replace(/\-/g, "+")
+         .replace(/_/g, "/");
+    let str = atob(d);
+    let a = Array.prototype.map.call(str, (x) => x.charCodeAt(0));
+    let h = a.reduce((prev, next) => prev + padStart(next.toString(16), 2, "0"), "");
+    console.log(h);
+  });
+  crypto.subtle.exportKey("raw", kp.publicKey).then((ab) => {
+    let v = new Uint8Array(ab);
+    let u = v.slice(0, 33);  // +1 here for the compressed point
+    u[0] = 2 + (v[v.length - 1] & 1);
+    let s = String.fromCharCode.apply(null, u);
+    console.log("/msg nickserv set property pubkey", btoa(s));
+  });
+});
+}}}
+
+You should see output like this:
+
+{{{
+Promise { <state>: "pending" }
+<priv-key>
+/msg nickserv set property pubkey <pub-key>
+}}}
+
+Copy the command starting with `/msg nickserv` and run it on the server.
+
+Then, copy the private key (middle line) to the preference `messenger.account.accountN.ecdsa` in the config editor in Tor Messenger, replacing N with the account number corresponding to the IRC account with which you want to use it.
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