Edit 04/01/18: Ethereum Wallet Cracking Pt 2. – GPU vs CPU can be found here
hashcat v3.6.0 was released yesterday and one of the newly supported hashes was Ethereum wallets (Go Ethereum (Geth), Mist and MyEtherWallet variants). This guide will show how a MyEtherWallet JSON keystore file is broken down, how it’s mapped to a hashcat compatible format, and finally an example crack.
First let’s get our wallet. That’s as easy as going to MyEtherWallet, entering a password, clicking generate and downloading it. MyEtherWallet suggests you “enter a strong password (at least 9 characters)”. Firstly this isn’t a suggestion it won’t let you generate your wallet unless your it’s at least 9 characters. Secondly, I wouldn’t say 9 characters is particularly strong, but that’s an argument for another day. If you don’t set a wallet name, a default is provided (as ours is) which comprises of the UTC time/date generated, followed by your new Ethereum wallet address.
Our wallet’s password is P@ssw0rd1! and the generated keystore file can be found below which is coloured to show how it’s mapped to the hashcat compatible format.
So from the above we can derive the following hashcat structure…
EDIT (17/07/17): Despite documentation showing the above structure due to transitions between ethereum2john versions, hashcat will accept both $ethereum$s*n*r*p*salt*ciphertext*mac (as shown in this example) and $ethereum$s*n*r*p*salt*mac*ciphertext formats.
…where s references scrypt variant in this instance. The letter p could also be found which indicates it’s a PBKDF2 variant. Fortunately ethereum2john.py makes the hashcat prep easy (you heard me right, ethereum2john for hashcat prep… ether2hashcat was superseded by it) by just pointing it at the wallet as shown below.
Now we’ve got the hash we can pass it over to hashcat. As we’ve got an scrypt based hash a quick lookup shows the required hashcat mode is 15700.
hashcat64.exe -m15700 $ethereum$s*1024*8*1*437964c9bd1b5f63bde56560808c894792f8f670694590b776e22381e32dd33b*7f5c865554d67604394ae54d7a4f9735bdb85c90e606a672d18add1d167d793b*96f2a849321cc04cb6c0fcee1bd4b195ca681ca28064dc45000f02e47230c5b6 b:\Dictionaries\rockyou.txt --status --status-timer=5 -w3 -r rules\hob064.rule
3 mins 41 secs @ circa 2200 H/s, job done. FYI this laptop has a mobile GTX 1060.
A couple of general password cracking points to note here…
- The password – P@ssw0rd1! isn’t in the standard rockyou dictionary so assuming this dictionary is being used (and commonly is), a non-rule based attack wouldn’t have cracked it.
- The rule – They’re important, as I literally just said above 😀 . Algorithm complexity should always be a factor when choosing one. For example, I throw bigger rule sets against fast hashes (e.g. MD5, NTLM) as the speed you’ll crack at will exhaust the larger rule set quicker. As Ethereum scrypt hashes are heinously slow, I’ll throw smaller, more efficient rule sets (relative to size) against it first.
The hob064 rule set used above is very efficient and good first choice when attacking complex algorithms. I’ve already written about hashcat rule efficiency on NotSoSecure’s blog (where you’ll note the most efficient rule tested was hob064). When attacking fast hashes I tend to use my own larger custo m rule, derived from a number of high performing rules against a large hash set. This custom rule was created from the testing noted in the above linked blog, and can be found here if you want to give it a go… although you’ll be waiting a while if you throw it against an Ethereum wallet with a good password!
Edit 04/01/18: A follow up covering why hashcat can crash on Ethereum wallets and GPU/CPU differences can be found in part 2.