5 ms·

So, being one of the people who hovers around laymanship when it comes to these questions, how hard is it to crack a randomly generated 25 character string with

So, being one of the people who hovers around laymanship when it comes to these questions, how hard is it to crack a randomly generated 25 character string with 5 digits and 5 symbols? This is typically what I would use for a website.

chronial 10y ago
How do you randomly generate these passwords?
- iimpact 10y ago
  password managers
  - sbierwagen 10y ago
    Tinfoil hat time: if your password manager uses a bad generation scheme or backdoored RNG like Dual EC, then its passwords might be much easier to crack than they would appear. https://en.wikipedia.org/wiki/Dual_EC_DRBG https://en.wikipedia.org/wiki/Dual_EC_DRBG
    - dwightgunning 10y ago
      This is always my concern. At some point the password managers become an interesting attack vector. Why can't people just be nice.
    - bigiain 10y ago
      I know you covered yourself with the tinfoil disclaimer, but Ima take you seriously here for a thought experiment... I wonder if that's actually a risk? At least for people not being individually targeted? A random Elbonian hacker who gets a dump of 117 million password hashes has (at least) three approaches she can take to make use of it - she can run oclHashcat or JtR using a good wordlist (say, Hashkiller or phpbb) and a reasonable ruleset to tweak them, which'll fairly quickly reveal common, reused, or guessable passwords in hours/days/weeks - or she can set it to enumerate through an entire $howeverymany bit password space, which is guaranteed to find all the passwords but not before the heat death of the universe... Or she could try only the selections out of that random keyspace that a flawed version of FooPasswordSafe is capable of generating. I'm not sure how long the last approach would take, but it'd have to be both a pretty flawed PRNG and a very widely used password safe for it to come anywhere near as useful as approach 1. (If she's only cracking the hash for the sbeirwagen@gmail.com record, things are somewhat different to if she's just trying to find _any_ "useable" passwords out of 117 million... And if she _knows_ sbeirwagen uses DudPasswordSafe.exe, it's likely she knows better ways of attempting to acquire your password than hoping to crack it from publicly released credential dumps...)
- Esau 10y ago
  Personally, I like to use Diceware to create random character strings. http://world.std.com/~reinhold/dicewarefaq.html#randomstrings http://world.std.com/~reinhold/dicewarefaq.html#randomstring... I even bought a set of casino dice.
- addled 10y ago
  I like the password generator and virtual dice roller on https://www.random.org https://www.random.org, but I guess it requires one to trust their claims that they are getting numbers from atmospheric noise and not a PRNG secretly.
  - TheDong 10y ago
    More importantly, that's over the network so you have to trust the site to not log what it gives back, every CA to not have issued a false cert for them (allowing them to be trivially MITMd), and all software that runs on your computer to boot. The "PRNG" vs "Real RNG" boogeyman scare is such a load of horseshit. The whole point of modern PRNGs is that they're good enough computers can't detect patterns. I assure you that you're gaining zero security by using random.org vs openssl rand... and in fact, you're losing massive amounts of security because it's going over the network.
    - throwaway7767 10y ago
      Minor nitpick: you should replace "PRNG" with "cryptographically secure PRNG". Not all PRNG methods are aiming for the standard of "computers can't detect patterns", for example the common Mersenne Twister PRNG would not be a good choice to generate crypto keys or passwords. You're right that using an internet service like that to generate passwords is insane, and there is no need for some fancy custom RNG hardware just to generate some keys/passwords.
- beberlei 10y ago
  you can install a tool "pwgen" on linux machines that will generate you passwords, configurable with size and types of characters included. pwgen -y 40 1 Generates one password with 40 chars, including special chars (-y).
  - pdw 10y ago
    head -c 24 /dev/urandom | base64 will give you a password with 24 * 8 = 192 random bits.
garethrees 10y ago
Such a password has about 157 bits of entropy, which is far too big to be found by any kind of brute-force approach. Of course there are other ways that a password can be cracked, for example an attacker who breaks into the server can capture it as it is submitted. So it's still worth having a different password for each site.
- Freaky 10y ago
  > Such a password has about 157 bits of entropy, which is far too big to be found by any kind of brute-force approach. To put this into perspective: If you turned every grain of sand on Earth (about eight quintillion) into a computer able to test 1 trillion passwords per second, you'd need about 360 million years to exhaust half the search space and have better than even odds of guessing it.
wglb 10y ago
That is a good choice, and it is what I recommend to whoever will listen to me, and a few that won't. I use and recommend 1Password. To evaluate a password manager, check this page https://discussions.agilebits.com/discussion/15416/1password-and-the-crypto-wars https://discussions.agilebits.com/discussion/15416/1password... for good questions to ask. For example, what data they can turn over, what their encryption practices are. Key phrase: "There is no data of yours that we keep, so there is nothing to turnover". This can't be said by all password managers.
- bad_user 10y ago
  That's an old and outdated page. 1Password has moved to a subscription model, thus storing the encrypted database themselves. The old "offline" option is still around, but it has been deemphasized, for one because they stopped implementing features supporting it (like an offline HTML interface for opvault, or sync with other clouds besides Dropbox). Even more upsetting is that the standalone version is now much more expensive than it was. They did that to increase the attractiveness of their subscriptions of course. And the writing is on the wall really.
  - wglb 10y ago
    Well not quite. While they have added a subscription model, there is still the desktop-only version that works in accordance with that page. I didn't notice an increase in their price--I have one at home and one from work.
xapata 10y ago
Depends on how that password is stored. Mostly. Your alphabet, lowercase + uppercase + digits + symbols, has 72 characters. There are 72 ways to pick the first character of your password, 72 ways to pick the second, etc. So there are 72 to the 25th power possible passwords, about 7.5 times 10 to the 46th (about 7 followed by 46 zeroes). That's fewer possibilities than the number of atoms in the universe and fewer possibilities than the ways you can order a deck of cards, but if a computer can calculate one hash per nanosecond, it'd take about ... well, more millennia than I know the words for. Even if we're talking about a cluster of GPU machines, it's effectively forever. Unless you had some infinite improbability drive (like a quantum computer?) and you guess correctly on the first try. So what did you use to generate the random password? Did you use your favorite programming language's pseudo-random number generator? Remember, "anyone who attempts to generate random numbers by deterministic means is, of course, living in a state of sin" (John von Neumann). A bad random number generator might only have 2^32 possibilities. Let's put that aside. It's unlikely that the hacker knows which random number generator you used. It's much more likely that the company storing your passwords is not storing them securely. Passwords should not be stored, ever. Instead, the company should store a hashcode. The hashing algorithm should be like the butterfly effect -- a tiny change in the password produces an unpredictable difference in the hashcode. Unfortunately, many older hashing algorithms, like MD5, are predictable. A hacker can find an MD5 collision -- not your password, but one that hashes to the same hashcode -- within minutes. There's more to it, but my advice is NEVER rely on password security by itself. If you care about your security, then use 2-factor authentication or physical security in combination with password protection. Edit: Am I incorrect? I see there was a downvote. Please educate me.
eru 10y ago
Do you actually generate your strings randomly, or do you rely on yourself, a puny human I suppose, to generate it?

chronial 10y ago

How do you randomly generate these passwords?

iimpact 10y ago
password managers
- sbierwagen 10y ago
  Tinfoil hat time: if your password manager uses a bad generation scheme or backdoored RNG like Dual EC, then its passwords might be much easier to crack than they would appear. https://en.wikipedia.org/wiki/Dual_EC_DRBG https://en.wikipedia.org/wiki/Dual_EC_DRBG
  - dwightgunning 10y ago
    This is always my concern. At some point the password managers become an interesting attack vector. Why can't people just be nice.
  - bigiain 10y ago
    I know you covered yourself with the tinfoil disclaimer, but Ima take you seriously here for a thought experiment... I wonder if that's actually a risk? At least for people not being individually targeted? A random Elbonian hacker who gets a dump of 117 million password hashes has (at least) three approaches she can take to make use of it - she can run oclHashcat or JtR using a good wordlist (say, Hashkiller or phpbb) and a reasonable ruleset to tweak them, which'll fairly quickly reveal common, reused, or guessable passwords in hours/days/weeks - or she can set it to enumerate through an entire $howeverymany bit password space, which is guaranteed to find all the passwords but not before the heat death of the universe... Or she could try only the selections out of that random keyspace that a flawed version of FooPasswordSafe is capable of generating. I'm not sure how long the last approach would take, but it'd have to be both a pretty flawed PRNG and a very widely used password safe for it to come anywhere near as useful as approach 1. (If she's only cracking the hash for the sbeirwagen@gmail.com record, things are somewhat different to if she's just trying to find _any_ "useable" passwords out of 117 million... And if she _knows_ sbeirwagen uses DudPasswordSafe.exe, it's likely she knows better ways of attempting to acquire your password than hoping to crack it from publicly released credential dumps...)
Esau 10y ago
Personally, I like to use Diceware to create random character strings. http://world.std.com/~reinhold/dicewarefaq.html#randomstrings http://world.std.com/~reinhold/dicewarefaq.html#randomstring... I even bought a set of casino dice.
addled 10y ago
I like the password generator and virtual dice roller on https://www.random.org https://www.random.org, but I guess it requires one to trust their claims that they are getting numbers from atmospheric noise and not a PRNG secretly.
- TheDong 10y ago
  More importantly, that's over the network so you have to trust the site to not log what it gives back, every CA to not have issued a false cert for them (allowing them to be trivially MITMd), and all software that runs on your computer to boot. The "PRNG" vs "Real RNG" boogeyman scare is such a load of horseshit. The whole point of modern PRNGs is that they're good enough computers can't detect patterns. I assure you that you're gaining zero security by using random.org vs openssl rand... and in fact, you're losing massive amounts of security because it's going over the network.
  - throwaway7767 10y ago
    Minor nitpick: you should replace "PRNG" with "cryptographically secure PRNG". Not all PRNG methods are aiming for the standard of "computers can't detect patterns", for example the common Mersenne Twister PRNG would not be a good choice to generate crypto keys or passwords. You're right that using an internet service like that to generate passwords is insane, and there is no need for some fancy custom RNG hardware just to generate some keys/passwords.
beberlei 10y ago
you can install a tool "pwgen" on linux machines that will generate you passwords, configurable with size and types of characters included. pwgen -y 40 1 Generates one password with 40 chars, including special chars (-y).
- pdw 10y ago
  head -c 24 /dev/urandom | base64 will give you a password with 24 * 8 = 192 random bits.

garethrees 10y ago

Such a password has about 157 bits of entropy, which is far too big to be found by any kind of brute-force approach. Of course there are other ways that a password can be cracked, for example an attacker who breaks into the server can capture it as it is submitted. So it's still worth having a different password for each site.

Freaky 10y ago
> Such a password has about 157 bits of entropy, which is far too big to be found by any kind of brute-force approach. To put this into perspective: If you turned every grain of sand on Earth (about eight quintillion) into a computer able to test 1 trillion passwords per second, you'd need about 360 million years to exhaust half the search space and have better than even odds of guessing it.

wglb 10y ago

That is a good choice, and it is what I recommend to whoever will listen to me, and a few that won't. I use and recommend 1Password. To evaluate a password manager, check this page https://discussions.agilebits.com/discussion/15416/1password-and-the-crypto-wars https://discussions.agilebits.com/discussion/15416/1password... for good questions to ask. For example, what data they can turn over, what their encryption practices are. Key phrase: "There is no data of yours that we keep, so there is nothing to turnover". This can't be said by all password managers.

bad_user 10y ago
That's an old and outdated page. 1Password has moved to a subscription model, thus storing the encrypted database themselves. The old "offline" option is still around, but it has been deemphasized, for one because they stopped implementing features supporting it (like an offline HTML interface for opvault, or sync with other clouds besides Dropbox). Even more upsetting is that the standalone version is now much more expensive than it was. They did that to increase the attractiveness of their subscriptions of course. And the writing is on the wall really.
- wglb 10y ago
  Well not quite. While they have added a subscription model, there is still the desktop-only version that works in accordance with that page. I didn't notice an increase in their price--I have one at home and one from work.

xapata 10y ago

Depends on how that password is stored. Mostly. Your alphabet, lowercase + uppercase + digits + symbols, has 72 characters. There are 72 ways to pick the first character of your password, 72 ways to pick the second, etc. So there are 72 to the 25th power possible passwords, about 7.5 times 10 to the 46th (about 7 followed by 46 zeroes). That's fewer possibilities than the number of atoms in the universe and fewer possibilities than the ways you can order a deck of cards, but if a computer can calculate one hash per nanosecond, it'd take about ... well, more millennia than I know the words for. Even if we're talking about a cluster of GPU machines, it's effectively forever. Unless you had some infinite improbability drive (like a quantum computer?) and you guess correctly on the first try. So what did you use to generate the random password? Did you use your favorite programming language's pseudo-random number generator? Remember, "anyone who attempts to generate random numbers by deterministic means is, of course, living in a state of sin" (John von Neumann). A bad random number generator might only have 2^32 possibilities. Let's put that aside. It's unlikely that the hacker knows which random number generator you used. It's much more likely that the company storing your passwords is not storing them securely. Passwords should not be stored, ever. Instead, the company should store a hashcode. The hashing algorithm should be like the butterfly effect -- a tiny change in the password produces an unpredictable difference in the hashcode. Unfortunately, many older hashing algorithms, like MD5, are predictable. A hacker can find an MD5 collision -- not your password, but one that hashes to the same hashcode -- within minutes. There's more to it, but my advice is NEVER rely on password security by itself. If you care about your security, then use 2-factor authentication or physical security in combination with password protection. Edit: Am I incorrect? I see there was a downvote. Please educate me.

eru 10y ago

Do you actually generate your strings randomly, or do you rely on yourself, a puny human I suppose, to generate it?