5 ms·

> it would still be feasible to crack a single user's password if it was weak enough I'm sorry, but how? You'd need data centers worth of effort for many year

by Achshar 10y ago

> it would still be feasible to crack a single user's password if it was weak enough I'm sorry, but how? You'd need data centers worth of effort for many years.

OskarS 10y ago
They say that the bcrypt hashing takes 100 ms on their servers. If we take that as our limitations, it means we can try 10 passwords per second. So if you had a dictionary of common passwords, plus the salt, you could try 36000 passwords per hour. If the password is "password12345" (hence "weak enough"), you could feasibly crack that. (I should say I'm not a professional security engineer so I'm probably wrong about everything and would appreciate corrections. )
- Someone1234 10y ago
  Great analysis (that in my experience is largely accurate). Just want to tack on one footnote: 100 ms is based on a single CPU core. Most CPUs have 4-8 cores. So instead of 10 passwords a second you could argue 40-80 passwords a second is believable with concurrent operations (which all popular hash cracking software supports). It is definitely viable to break a single user's hashed password no matter what the scheme or work factor. Strong hashing algorithms with high work factors just stop you breaking multiple user's passwords quickly (and gives you 1-3 days of delay). It is a stop gap, not impenetrable defence like some believe. All technical people need to take a day and learn how to break password hashes. Not just the theory, but go download the software and actually do it.
  - ZoFreX 10y ago
    > Not just the theory, but go download the software and actually do it. And now that hashcat and oclhashcat have merged[1] and are open-source[2] it's never been easier to install hashcat and start cracking passwords! [1] https://hashcat.net/forum/thread-5559.html https://hashcat.net/forum/thread-5559.html [2] https://hashcat.net/forum/thread-4880.html https://hashcat.net/forum/thread-4880.html
- Dylan16807 10y ago
  Specifically, if you took the top 10k passwords from this blog post as a starting point you would be able to crack "password123" in under a minute.
raverbashing 10y ago
Bcrypt with a high work factor is useless if your password is still 12345

by Achshar 10y ago

> it would still be feasible to crack a single user's password if it was weak enough I'm sorry, but how? You'd need data centers worth of effort for many years.

OskarS 10y ago

They say that the bcrypt hashing takes 100 ms on their servers. If we take that as our limitations, it means we can try 10 passwords per second. So if you had a dictionary of common passwords, plus the salt, you could try 36000 passwords per hour. If the password is "password12345" (hence "weak enough"), you could feasibly crack that. (I should say I'm not a professional security engineer so I'm probably wrong about everything and would appreciate corrections. )

Someone1234 10y ago
Great analysis (that in my experience is largely accurate). Just want to tack on one footnote: 100 ms is based on a single CPU core. Most CPUs have 4-8 cores. So instead of 10 passwords a second you could argue 40-80 passwords a second is believable with concurrent operations (which all popular hash cracking software supports). It is definitely viable to break a single user's hashed password no matter what the scheme or work factor. Strong hashing algorithms with high work factors just stop you breaking multiple user's passwords quickly (and gives you 1-3 days of delay). It is a stop gap, not impenetrable defence like some believe. All technical people need to take a day and learn how to break password hashes. Not just the theory, but go download the software and actually do it.
- ZoFreX 10y ago
  > Not just the theory, but go download the software and actually do it. And now that hashcat and oclhashcat have merged[1] and are open-source[2] it's never been easier to install hashcat and start cracking passwords! [1] https://hashcat.net/forum/thread-5559.html https://hashcat.net/forum/thread-5559.html [2] https://hashcat.net/forum/thread-4880.html https://hashcat.net/forum/thread-4880.html
Dylan16807 10y ago
Specifically, if you took the top 10k passwords from this blog post as a starting point you would be able to crack "password123" in under a minute.

raverbashing 10y ago

Bcrypt with a high work factor is useless if your password is still 12345