Remove timestamp — 24-word mnemonic alone is sufficient for recovery

keygen.py

@@ -2,35 +2,22 @@
 """
 SSH key generator with BIP39 mnemonic backup.
 
-generate  — creates a new Ed25519 SSH key pair and prints 24 recovery words + timestamp
-recover   — re-creates the exact same key pair from those 24 words + timestamp
+generate  — creates a new Ed25519 SSH key pair and prints 24 recovery words
+recover   — re-creates the exact same key pair from those 24 words
 """
 
 import argparse
 import getpass
 import os
 import sys
-from datetime import datetime, timezone
 from pathlib import Path
 
-from cryptography.hazmat.primitives import hashes, serialization
+from cryptography.hazmat.primitives import serialization
 from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
-from cryptography.hazmat.primitives.kdf.hkdf import HKDF
 from mnemonic import Mnemonic
 
 
 ENTROPY_BITS = 256  # → 24 BIP39 words
-TIMESTAMP_FORMAT = "%Y-%m-%d %H:%M:%S UTC"
-
-
-def derive_seed(entropy: bytes, timestamp: str) -> bytes:
-    """Derive 32-byte Ed25519 seed from mnemonic entropy + timestamp."""
-    return HKDF(
-        algorithm=hashes.SHA256(),
-        length=32,
-        salt=timestamp.encode(),
-        info=b"ssh-seed-keygen v1",
-    ).derive(entropy)
 
 
 def save_keypair(
@@ -113,25 +100,11 @@ def ask_passphrase(confirm: bool = True) -> bytes | None:
     return passphrase.encode()
 
 
-def ask_timestamp() -> str:
-    print(f"Generation timestamp (format: YYYY-MM-DD HH:MM:SS UTC):")
-    raw = input("Timestamp: ").strip()
-    try:
-        datetime.strptime(raw, TIMESTAMP_FORMAT)
-    except ValueError:
-        print(f"Error: timestamp must match format '{TIMESTAMP_FORMAT}'", file=sys.stderr)
-        sys.exit(1)
-    return raw
-
-
 def cmd_generate(args: argparse.Namespace) -> None:
     mnemo = Mnemonic("english")
     entropy = os.urandom(ENTROPY_BITS // 8)
     words = mnemo.to_mnemonic(entropy)
-    timestamp = datetime.now(timezone.utc).strftime(TIMESTAMP_FORMAT)
-
-    seed = derive_seed(entropy, timestamp)
-    private_key = Ed25519PrivateKey.from_private_bytes(seed)
+    private_key = Ed25519PrivateKey.from_private_bytes(entropy)
 
     passphrase = ask_passphrase(confirm=True) if args.passphrase else None
 
@@ -144,10 +117,9 @@ def cmd_generate(args: argparse.Namespace) -> None:
     if passphrase:
         print("  Passphrase  : set")
 
-    print(f"\nWrite ALL of the following down — you need both to recover your key:\n")
-    print(f"  Timestamp : {timestamp}\n")
+    print(f"\nYour 24-word recovery mnemonic — write these down and store offline:\n")
     print(format_mnemonic(words))
-    print("\nKeep these secret. Both the words and the timestamp are required to recover.")
+    print("\nThese words reconstruct your exact private key. Keep them secret.")
 
 
 def cmd_recover(args: argparse.Namespace) -> None:
@@ -165,11 +137,8 @@ def cmd_recover(args: argparse.Namespace) -> None:
         print("Error: invalid mnemonic — check spelling or word count.", file=sys.stderr)
         sys.exit(1)
 
-    timestamp = ask_timestamp()
-
     entropy = bytes(mnemo.to_entropy(words))
-    seed = derive_seed(entropy, timestamp)
-    private_key = Ed25519PrivateKey.from_private_bytes(seed)
+    private_key = Ed25519PrivateKey.from_private_bytes(entropy)
 
     passphrase = ask_passphrase(confirm=True) if args.passphrase else None
 
@@ -210,7 +179,7 @@ def build_parser() -> argparse.ArgumentParser:
         "generate",
         aliases=["gen"],
         parents=[shared],
-        help="generate a new SSH key pair and print its 24-word mnemonic + timestamp",
+        help="generate a new SSH key pair and print its 24-word mnemonic",
     )
     sub.add_parser(
         "recover",