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Questions tagged [authentication]

the process of establishing the authenticity of a person or other entity. Not to be confused with authorization - defining access rights to resources.

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615 votes
23 answers
149k 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 ...
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552 votes
3 answers
98k views

Why can I log in to my Facebook account with a misspelled email/password?

I've been playing around with different login forms online lately to see how they work. One of them was the Facebook login form. When I logged out of my account my email and password were ...
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497 votes
8 answers
494k 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 ...
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  • 13k
396 votes
10 answers
271k 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?
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  • 4,113
391 votes
4 answers
493k views

Why is 'Bearer' required before the token in 'Authorization' header in a HTTP request?

What exactly is the difference between following two headers: Authorization : Bearer cn389ncoiwuencr vs Authorization : cn389ncoiwuencr All the sources which I have gone through, sets ...
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  • 4,011
295 votes
7 answers
81k views

What's the rationale behind Ctrl-Alt-Del for login

Why is Ctrl+Alt+Del required at login on certain Windows systems (I have not seen it elsewhere, but contradict me if I'm wrong) before the password can be typed in? From a usability point of view, it'...
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  • 2,879
259 votes
4 answers
162k 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 ...
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245 votes
17 answers
29k 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 ...
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  • 4,227
238 votes
4 answers
409k views

What is the difference between authorized_keys and known_hosts file for SSH?

I am learning the basics of SSH protocol. I am confused between the contents of the following 2 files: ~/.ssh/authorized_keys: Holds a list of authorized public keys for servers. When the client ...
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  • 2,593
235 votes
3 answers
34k views

Why did I have to wave my hand in front of my ID card?

I recently had to authenticate myself online to use an internet-based service. The authentication process was done via video call with me holding my ID card in front of my laptop camera beside my face....
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223 votes
13 answers
27k views

Is there any reason to not show users incorrectly entered passwords after a successful login?

Our client has come up with the requirement that in case the username in question has had multiple failed login attempts, the incorrectly entered password(s) must be shown once a successful login is ...
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  • 2,043
203 votes
4 answers
62k views

Is a rand from /dev/urandom secure for a login key?

Lets say I want to create a cookie for a user. Would simply generating a 1024 bit string by using /dev/urandom, and checking if it already exists (looping until I get a unique one) suffice? Should I ...
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  • 5,134
189 votes
4 answers
199k views

Is Plaid, a service which collects user’s banking login information, safe to use?

I recently signed up for Privacy.com, which uses a service called Plaid to link a bank account. To do this, it requires the user to provide their banking username and password to a webpage from Plaid,...
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  • 2,469
168 votes
7 answers
97k views

Difference Between OAUTH, OpenID and OPENID Connect in very simple term?

I am very confused the difficult jargon available in web about OAUTH, OpenID and OPENID Connect. Can anyone tell me the difference in simple words.
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  • 2,449
165 votes
8 answers
58k views

Why is Mother’s Maiden Name still used as a security question?

From time to time, some web sites asks to enter a security question and an answer for it. The question list is standard and it usually includes "What is your mother's maiden name?". Some people use ...
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  • 2,183
152 votes
11 answers
86k views

https security - should password be hashed server-side or client-side?

I am building a web application which requires users to login. All communication goes through https. I am using bcrypt to hash passwords. I am facing a dilemma - I used to think it is safer to make a ...
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  • 1,755
138 votes
10 answers
311k 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 ...
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  • 16.1k
137 votes
8 answers
67k 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 ...
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133 votes
6 answers
47k views

How secure are the FIDO U2F tokens

Google and Yubico just announced the availability of cryptographic security tokens following the FIDO U2F specification. Is this just another 2FA option, or is this significantly better than solutions ...
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  • 81.9k
131 votes
20 answers
34k views

How should I securely type a password in front of a lot of people?

I am a manager in an office where the company does not provide a company email, so I use my personal email. Often, I will receive jobs lists by email from my general manager. How should I log in to ...
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123 votes
3 answers
173k views

Session Authentication vs Token Authentication

I am trying to get a handle on some terms and mechanisms and find out how they relate to each other or how they overlap. Authenticating a theoretical web application and mobile application is the ...
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  • 2,705
116 votes
13 answers
28k views

Is it good or bad practice to allow a user to change their username?

I have looked all over online as well as this site to try to find out more information regarding the security of this, but haven't found anything. In my particular case, the product is a website, but ...
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  • 1,053
112 votes
9 answers
43k 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? ...
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  • 1,959
111 votes
13 answers
22k views

Secure way to log in to a website on someone else's computer

Suppose I am in a situation that I am forced to log in to my account using someone else's computer. Is there any secure way to do that so that I would be sure that my login details (i.e. password) are ...
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  • 1,081
111 votes
7 answers
127k views

What is the difference between Federated Login and Single Sign On?

What is the difference between Federated Login and Single Sign On authentication methods?
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  • 1,213
109 votes
11 answers
37k 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 ...
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  • 1,345
107 votes
17 answers
25k views

Is "password knocking" a good idea?

With port knocking, you have to "knock" on specific ports in defined order to expose a port on which service is running. How about password knocking? For example you have three passwords: A, B and C. ...
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  • 1,289
107 votes
2 answers
19k views

Is a redirect showing the password in plain text a security vulnerability?

A couple of days ago, I attempted to log into the website of a well-known SaaS provider. I used a password manager on my browser (so user/pass were correct) and the NoScript plugin which had limited ...
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  • 1,023
107 votes
5 answers
138k views

Should we store accesstoken in our database for oauth2?

I have a requirement to implement Facebook and Google login in my web application. I also need to access a user's Facebook/Google+ friend list. I have gone through the complete OAuth2 documentation of ...
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105 votes
7 answers
144k 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 ...
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  • 1,247
103 votes
12 answers
69k views

Why is client-side hashing of a password so uncommon?

There are very few websites that hash the users password before submitting it to the server. Javascript doesn't even have support for SHA or other algorithms. But I can think of quite a few ...
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  • 1,143
101 votes
5 answers
32k views

How can my employer be a man-in-the-middle when I connect to Gmail? [duplicate]

I'm trying to understand SSL/TLS. What follows are a description of a scenario and a few assumptions which I hope you can confirm or refute. Question How can my employer be a man-in-the-middle when ...
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  • 1,134
101 votes
3 answers
147k views

Token-based authentication - Securing the token

I have developed a backend REST API for a mobile app and I am now looking to implement token-based authentication for it to avoid having to prompt the user to login on every run of the app. What I ...
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  • 1,698
100 votes
4 answers
119k 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 ...
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98 votes
13 answers
31k views

Is a 6 digit numerical password secure enough for online banking?

My bank went through a major redesign of their customer online banking system recently. The way security is managed across the platform was also reviewed. The password I am able to set now to log in ...
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  • 963
92 votes
9 answers
17k views

Does anybody not store salts?

We talked about password hashing and salting in class today. Our professor had a very different understanding of the use case of salts from mine and said that you might not store the salt at all and ...
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  • 1,039
92 votes
9 answers
19k views

Is it possible make brute-force attacks ineffective by giving false positive answers to failed log-in attempts?

I don't have any experience or scientific knowledge in security, I just wanted to ask if this is possible because I am interested in it. What if I encrypt data and every password decrypts it, but ...
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  • 891
90 votes
4 answers
65k 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 ...
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  • 1,003
89 votes
7 answers
97k views

How do I secure my REST API?

In detail here's the problem: I'm building an Android app, which consumes my REST API on the back-end. I need to build a Registration and Login API to begin with. After searching with Google for a ...
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  • 993
80 votes
10 answers
44k views

Generic error message for wrong password or username - is this really helpful?

It is really common (and I would say it is some kind of security basic) to not show on the login page if the username or the password was wrong when a user tries to log in. One should show a generic ...
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  • 903
80 votes
3 answers
87k views

What are the dangers of allowing "less secure apps" to access my Google account?

According to https://support.google.com/accounts/answer/6010255: Google may block sign in attempts from some apps or devices that do not use modern security standards. Since these apps and devices ...
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  • 906
79 votes
3 answers
17k views

Does correcting misspelled usernames create a security risk?

Does correcting a misspelled username and prompting the user with a valid username introduce a security risk? I recently tried logging into facebook and misspelled my email. They prompted me with ...
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  • 865
79 votes
4 answers
10k views

Can an identity provider impersonate me? (Can Facebook post Stack Overflow questions under my name?)

There are multiple mechanisms (some now defunct) that allow me to access service A (the Relying Party / RP) using a token granted by service B (the Identity Provider / IdP). Typically these replace a ...
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  • 3,530
78 votes
6 answers
15k views

Is face recognition a good security feature?

I found that this guy uploaded some face recognition code with a comment that he'd like to use it "as a security feature". This got me thinking; is face recognition a valid security feature, or is it "...
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77 votes
7 answers
29k views

Is it unsafe to show message that username/account does not exist at login? [duplicate]

According to the OWASP Auth Guidelines, "An application should respond with a generic error message regardless of whether the user ID or password was incorrect. It should also give no indication to ...
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  • 888
76 votes
6 answers
18k 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 ...
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  • 3,372
76 votes
8 answers
11k views

Why is email often used as the ultimate verification?

In many services, email can be used to reset the password, or do something that is sensitive. Sensitive data is also quite often sent to you by email, e.g. long links that enable access to your ...
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76 votes
8 answers
14k views

What is the suggested best practice for changing a user's email address?

I recently jumped onto the hypetrain for an unnamed email service and am currently on my way to update all my accounts on various websites to get most of my (future) data off Google's Gmail. During ...
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  • 1,003
73 votes
8 answers
16k views

Is displaying remaining password retry count a security risk?

Some websites display a remaining password retry count when I input wrong passwords more than twice. For example, displaying that there are 3 retries remaining until locking out my account. Is this ...
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73 votes
9 answers
14k views

I almost searched my password, but didn't press enter. Is my password at risk, because of autocomplete or anything else?

Without even thinking about it, I typed my password into the Google search bar, but I didn't press enter. Since autocomplete is on, does that mean my password has been logged or indexed somewhere? ...
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