Authentication - establishing the authenticity of a person or other entity. Not to be confused with authorization - defining access rights to resources.
198
votes
16answers
19k views
How does changing your password every 90 days increase security?
Where I work I'm forced to change my password every 90 days. This security measure has been in place in many organizations for as long as I can remember. Is there a specific security vulnerability ...
138
votes
18answers
7k views
Passwords Being Sent in Clear Text Due to Users' Mistake in Typing it in the Username Field
Upon reviewing the Logs generated by different SIEMs (Splunk, HP Logger Trial and the AlienVault platform’s SIEM) I noticed that for some reason quite a few users tend to make the mistake of typing ...
113
votes
7answers
17k views
CTRL+ALT+DEL Login - Rationale behind it?
Maybe a rather noobish question: Why is CTRL+ALT+DEL required at login on Windows systems (I have not seen it elsewhere, but contradict me if I'm wrong) before the password can be typed in? From a ...
72
votes
3answers
43k views
RSA vs. DSA for SSH authentication keys
When generating SSH authentication keys on a Unix/Linux system with ssh-keygen, you're given the choice of creating a RSA or DSA key pair (using -t type).
What is the difference between RSA and DSA ...
62
votes
11answers
5k views
“Username and/or Password Invalid” - Why do websites show this kind of message instead of informing the user which one was wrong?
Lets say a user is logging into a typical site, entering their username and password, and they mistype one of their inputs. I have noticed that most, if not all, sites show the same message (something ...
48
votes
12answers
2k views
How do you log in from an unsecured computer?
Suppose that you are on a cybercafe, at a friend's home or at your work office, and you need to log in on a site, but you feel that the the computer can not be trusted (e.g. your friend isn't ...
41
votes
5answers
10k views
Certificate based authentication vs Username and Password authentication
What are the advantages and drawbacks of the certificate based authentication over username and password authentication?
I know some, but I would appreciate a structured and detailed answer.
UPDATE
...
35
votes
5answers
2k views
Do security questions subvert passwords?
Do security questions subvert hard to crack passwords? For example, if a site requires passwords with a certain scheme (length + required character sets) and has a security question, why would someone ...
34
votes
7answers
3k views
Are passwordless SSH logins more secure?
I had a long discussion with my co-workers whether key-based SSH authentication (particularly for OpenSSH) is more secure than authentication using passwords. My co-workers always connect to servers ...
34
votes
7answers
9k views
Is BASIC-Auth secure if done over HTTPS?
I'm making a REST-API and it's straight forward to do BASIC auth login. Then let HTTPS secure the connection so the password is protected when the api is used.
Can this be considered secure?
34
votes
4answers
6k views
Is posting from HTTP to HTTPS a bad practice?
Working on the assumption that SSL serves both to encrypt data and to provide assurance as to the identity and legitimacy of the website, should the practice of providing a logon form on a page ...
31
votes
2answers
3k views
Is a rand from /dev/urandom secure for a login key?
Lets say I want to cookie for a user, would simply going to /dev/urandom, generating a 1024 bit string, checking if it already exists (and looping till I get a unique one) suffice? Or should I be ...
30
votes
7answers
20k views
Where can I find good dictionaries for dictionary attacks?
I’m wondering where I can find good collections of dictionaries which can be used for dictionary attacks?
I've found some through Google, but I’m interested in hearing about where you get your ...
30
votes
5answers
4k views
What are the downsides of BrowserID/Persona compared to OpenID/OAuth/Facebook?
Mozilla went live with a new service called BrowserID/Persona (announcement, background). It is intended to replace current single-sign-on solutions such as OpenID, OAuth and Facebook.
One advantage ...
29
votes
9answers
1k views
Use additional “password” in Referer to hide private site?
I have a private (= I'm the only user) site at example.com/private/. Nothing else is published at this host (it's my domain).
I don't want anyone to know that there is anything at example.com, ...
28
votes
4answers
13k views
What is the difference between an x.509 “client certificate” and a normal SSL certificate?
I am setting up a web service through which my company will talk to a number of business customers' services. We will be exchanging information using SOAP. I would like to handle authentication with ...
27
votes
4answers
5k views
What is the use of a client nonce?
After reading Part I of Ross Anderson's book, Security Engineering, and clarifying some topics on Wikipedia, I came across the idea of Client Nonce (cnonce). Ross never mentions it in his book and I'm ...
26
votes
9answers
2k views
Isn't OAuth, OpenID, Facebook Connect, and others crazy from a security standpoint?
I work with APIs all the time and I work with web developers who insist that OAuth, OpenID, etc are far superior than a home-brew method. Every site seems to be using these as well now for ease of use ...
26
votes
5answers
4k views
How hard is it to intercept SMS (two-factor authentication)?
A lot of two-factor authentication mechanisms use SMS to deliver single-use passphrase to the user. So how secure is it? Is it hard to intercept the SMS message containing the passphrase? Do mobile ...
26
votes
3answers
659 views
What is this authentication method/approach called?
Background: I want to implement something like this in our websites, and I'm looking for advice and possibly APIs that allow this out of the box rather than re-inventing the wheel, but I can't even ...
24
votes
1answer
965 views
What's the risk if I accidently type my password into a username field (Windows logon)?
I'm used to logging into my personal Mac which is a password-only field (like waking from sleep mode). Sometimes I have to use a Windows network on which I have an account, but of course I have to ...
24
votes
5answers
2k views
How to Securely Implement a “Remember Me” Feature?
Assuming you already have a website that implements all of the standard login stuff, what is the correct and most secure way to allow users to automatically be logged in for a certain time period ...
23
votes
6answers
1k views
Is using a public-key for logging in to SSH any better than saving a password?
Using a public/private key pair is fairly convenient for logging in to frequented hosts, but if I'm using a key pair with no password, is that any safer (or less safe) than a password? The security ...
23
votes
4answers
1k views
Should I change the default SSH port on linux servers?
Is there any advantage in changing the SSH port, I've seen people do that, but I can't seem to find the reason why.
If you have a strong password and/or a certificate, is it useful for anything?
...
23
votes
5answers
2k views
How do some sites (e.g. online banks) only ask for specific characters from a password without storing it as plaintext?
I thought How can a system enforce a minimum number of changed characters... would answer my question, but it seems this is a different case.
When I sign on to my online banking account, I'm prompted ...
22
votes
3answers
994 views
Is authentication using personal pictures more secure than passwords?
Statement 1
There is a start up called PixelPin. On the web site it reads:
The PixelPin solution is simple and quick to use, yet very secure.
PixelPin eliminates the traditional alphanumeric ...
22
votes
2answers
3k views
I just send username and password over https. Is this ok?
When a user's logging in to my site, they send their username and password to me over https. Besides the ssl, there's no special obfuscation of the password - it lives in memory in the browser in the ...
21
votes
9answers
1k views
Why do some people really hate security via client-side?
For instance, lets look at a common login system for a website
HTTPS connection is made
User submits credentials via POST
Server-side code hashes the password and looks if it matches the user name
...
21
votes
4answers
5k views
How to achieve non-repudiation?
If I have a message that I need to send to another person, how do I achieve non repudiation ?
Is digitally signing the message sufficient ?
20
votes
9answers
1k views
How can I ensure that I connect to the right wireless Access Point?
Under Windows/Linux, client side. How can I ensure that I'm not connecting to a rogue AP?
Thank you!
20
votes
2answers
515 views
How does Google Authenticator work?
Google Authenticator is an alternative to SMS for 2Step verification, installing an app on Android where the codes will be sent.
It works without any connectivity; it even works on plane mode. This ...
20
votes
4answers
1k views
How is “something you have” typically defined for “two-factor” authentication?
A wide range of products claim to offer "two-factor authentication" (c.v. Two-factor authentication - Wikipedia). Most are deployed as "something you have" to be used in addition to a normal password ...
19
votes
9answers
612 views
What's a good way to trigger a hidden 'distress signal' in instant messaging?
Here's the scenario:
Alice and bob use Off-the-record messaging to communicate over IM. The have:
Encryption
Authentication
Deniability
Perfect forward secrecy
They communicate after ...
19
votes
11answers
921 views
Is it safe to use a weak password as long as I have two-factor authentication?
I'm careful to use strong passwords (according to How Big is Your Haystack, my passwords would take a massive cracking array 1.5 million centuries to crack), I don't reuse passwords across sites, and ...
19
votes
3answers
811 views
Am I wrong to believe that passwords should never be recoverable (one way hash)?
I recently forgot my password for our cable provider online account, only to discover that they sent it to us via plain text in an email. I quickly sent an email to customer support asking them if ...
19
votes
7answers
2k views
How to prevent cheating (extra votes) in online contests?
Mitigating Cheating & Voter Fraud in Online Contests…
We run online contests of various sorts that involve users voting on entries (usually one vote per user per day). The prizes range from ...
18
votes
6answers
793 views
How to secure a WiFi network?
What do I have to do to secure a WiFi network? Is there any best practices?
I have been recommended to use WPA2 encryption on the router, is that enough? What can I do to improve the security even ...
18
votes
4answers
425 views
How does using OpenID affect webapp security?
Using OpenID for authenticating users grows in popularity and, in fact, makes a webapp easier to use.
But what are the security considerations one should bear in mind when deciding whether to ...
18
votes
5answers
1k views
Should usernames be kept secret?
Help me settle an discussion among colleagues and guide future design:
Even in a high impact scenario: e.g. protecting payment application or government gateway but in an Internet accessible ...
18
votes
3answers
342 views
Isn't openid with http an issue?
Many openid enabled sites default to http identifiers, even if the openid provider supports https (such as myopenid.com).
Does this pose a threat beside the identity being exposed? The second step of ...
17
votes
6answers
1k views
Why do we ask for a user's existing password when changing their password?
In a web applications context, when a user wants to change their current password, generally they would have to enter their current password first. However at this point, the user has already been ...
17
votes
6answers
998 views
How to verify that someone is who they say they are online?
I am working on an online job application web app and the question has come up about how we will verify that someone submitting an application is who they say they are.
For example, we don't want ...
17
votes
8answers
739 views
How to protect against brute forcing
How do you properly implement defenses against brute forcing? Is it best to store how many times someone tried to log in and block them after X attempts? And how would "someone" be identified? With ...
17
votes
2answers
874 views
Sending temp password when users first registered - is that good for anything?
One of our clients has sent us a list of security requirements. One of them was that registration does not including setting a password - once complete, a temp password is sent to the user, and the ...
16
votes
3answers
4k views
What are the main advantages and disadvantages of webid compared to browserid?
What are the main advantages and disadvantages of webid compared to browserid?
This question is inspired by this answer which got a number of upvotes despite being very vague on the topic of that ...
15
votes
12answers
2k views
Why do we even use passwords / passphrases next to biometrics?
In the last couple of days there were a lot of talking about passwords and passphrases, not only here, but on several blogs and forums I follow (especially after XKCD #936 saw the light of this ...
15
votes
3answers
2k views
Should I have a maximum password length?
I'm creating a webapp, and part of my authentication method is password length.
Should I put one in place? (say, 50 characters?) Or should I just put a minimum length (Currently at 6).
Are there ...
15
votes
5answers
505 views
Safe way to authenticate (multi-factor authentication?) while being monitored?
(I'm trying for a bit more precise answer, particularly with regard to multi-factor authentication, than I received for "Safe way to use a computer that has spyware/keylogger installed?" on SU.)
...
14
votes
9answers
1k views
is there a safe way to login to my gmail account from a public pc?
Sometimes i need to use a public pc to access my gmail account, is there a safe way to login and keep my password safe in case there was a keylogger or a trojan on that pc? are there tools that could ...
14
votes
6answers
710 views
Why isn't open WiFi encrypted?
As far as I understand, WiFi networks that require no password send traffic through the air unencrypted. Those that require a password encrypt each connection uniquely, even if they're all using the ...
