BIP155: Mention SHA3-256 explicitly

Author: hebasto

bip-0155.mediawiki

@@ -170,6 +170,7 @@ onion_address = base32(PUBKEY | CHECKSUM | VERSION) + ".onion"
    - VERSION is an one byte version field (default value '\x03')
    - ".onion checksum" is a constant string
    - CHECKSUM is truncated to two bytes before inserting it in onion_address
+   - H() is the SHA3-256 cryptographic hash function
 </pre>
 
 Tor v3 addresses MUST be sent with the <code>TORV3</code> network ID, with the 32-byte PUBKEY part in the address field. As VERSION will always be '\x03' in the case of v3 addresses, this is enough to reconstruct the onion address.