Sessions are unreliable because they rely on cookies, CAPTCHAs are regularly broken [including ReCAPTCHA]. The only reliable method is deceptively simple: ask a question. Don’t use a math question because computers are surprisingly adept at solving those for some reason. Great old standbys are things like: What is the fourth word in the sixth paragraph … Read more
I saw a creative approach to this once… For each login attempt, that fails, the lockout time increases… exponentially. attempt | lockout time ====================== 1 | 2s 2 | 4s 3 | 8s 4 | 16s 5 | 32s 6 | 64s 7 | 128s 8 | 256s 9 | 512s 10 | 1024s In … Read more
Combining methods 3 and 4 from the original post into a kind of ‘fuzzy’ or dynamic whitelist, and then – and here’s the trick – not blocking non-whitelisted IPs, just throttling them to hell and back. Note that this measure is only meant to thwart this very specific type of attack. In practice, of course, … Read more
In your case, breaking the hash algorithm is equivalent to finding a collision in the hash algorithm. That means you don’t need to find the password itself (which would be a preimage attack), you just need to find an output of the hash function that is equal to the hash of a valid password (thus … Read more
I think database-persisted short lockout period for the given account (1-5 minutes) is the only way to handle this. Each userid in your database contains a timeOfLastFailedLogin and numberOfFailedAttempts. When numbeOfFailedAttempts > X you lockout for some minutes. This means you’re locking the userid in question for some time, but not permanently. It also means … Read more
Sharing my experience after trying everything available. 1- Smart word list attack from android-keystore-password-recover is what eventually worked for me after spending a day trying different lists. Unfortunately, it does not support multithreading and I couldn’t get it to run faster than 30,000 trials/second. I might contribute multithreading support to project soon. 2- KeystoreBrute was … Read more
Hiding a salt is unnecessary. A different salt should be used for every hash. In practice, this is easy to achieve by getting 8 or more bytes from cryptographic quality random number generator. From a previous answer of mine: Salt helps to thwart pre-computed dictionary attacks. Suppose an attacker has a list of likely passwords. … Read more