How to identify and crack a Double SHA-1 — sha1(sha1($pass)) hash

Double SHA-1 — sha1(sha1($pass)) is a raw / unsalted hash type. It is fast and typically unsalted, which makes weak passwords recoverable quickly on consumer GPU hardware. This page shows how to recognise it and the exact commands to attack it.

All identification runs locally in WebAssembly. The commands below write the hash to a local file on your machine — nothing is sent to this site.

Identifying the hash

The hash identifier on the home page detects Double SHA-1 — sha1(sha1($pass)) entirely in your browser — your hash is never uploaded. A typical example looks like this:

3109b810188fc9ece9f9573811baa02bde4e9cd0

Cracking Double SHA-1 — sha1(sha1($pass)) with hashcat

Save the hash to a file and run hashcat in mode -m 4500. Start with a wordlist such as rockyou.txt:

echo '3109b810188fc9ece9f9573811baa02bde4e9cd0' > hash.txt && hashcat -m 4500 hash.txt /usr/share/wordlists/rockyou.txt

Add a rule set to mutate dictionary words (capitalisation, leetspeak, appended digits) and dramatically widen coverage:

echo '3109b810188fc9ece9f9573811baa02bde4e9cd0' > hash.txt && hashcat -m 4500 hash.txt /usr/share/wordlists/rockyou.txt -r /usr/share/hashcat/rules/best64.rule