841
votes
23answers
168k views

XKCD #936: Short complex password, or long dictionary passphrase?

How accurate is this XKCD comic from August 10, 2011? I've always been an advocate of long rather than complex passwords, but most security people (at least the ones that I've talked to) are ...
715
votes
3answers
366k views

How does SSL/TLS work?

How does SSL work? I just realised we don't actually have a definitive answer here, and it's something worth covering. I'd like to see details in terms of: A high level description of the protocol....
529
votes
11answers
112k views

How to securely hash passwords?

If I hash passwords before storing them in my database, is that sufficient to prevent them being recovered by anyone? I should point out that this relates only to retrieval directly from the database,...
476
votes
20answers
62k views

How can I explain SQL injection without technical jargon?

I need to explain SQL injection to someone without technical training or experience. Can you suggest any approaches that have worked well?
471
votes
14answers
81k views

What technical reasons are there to have low maximum password lengths?

I have always wondered why so many websites have very firm restrictions on password length (exactly 8 characters, up to 8 characters, etc). These tend to be banks or other sites where I actually care ...
436
votes
22answers
93k 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 ...
400
votes
5answers
138k views

Do any security experts recommend bcrypt for password storage?

On the surface bcrypt, an 11 year old security algorithm designed for hashing passwords by Niels Provos and David Mazieres, which is based on the initialization function used in the NIST approved ...
356
votes
13answers
69k views

Are passwords stored in memory safe?

I just realized that, in any language, when you save a password in a variable, it is stored as plain text in the memory. I think the OS does its job and forbids processes from accessing each other's ...
354
votes
11answers
44k views

Is my developer's home-brew password security right or wrong, and why?

A developer, let's call him 'Dave', insists on using home-brew scripts for password security. See Dave's proposal below. His team spent months adopting an industry standard protocol using Bcrypt. ...
344
votes
12answers
64k views

Is it bad practice to use your real name online?

On some accounts I use my real name on-line (Google+/Facebook/Wikipedia/personal blog), others (Q&A/Gaming) I use an alias. My question is: Security and privacy wise, what can people do with my ...
335
votes
8answers
284k 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 ...
302
votes
22answers
295k views

I found that the company I work for is putting a backdoor into mobile phones

I have found out recently that the remote assistant software that we put in a smartphone we sell can be activated by us without user approval. We are not using this option, and it is probably there ...
298
votes
8answers
57k views

How to store salt?

Nowadays, if we expect to store user password securely, we need at least do the following thing $pwd=hash(hash($password) + salt) then store $pwd in your system instead of the real password. I have ...
293
votes
13answers
37k views

How is it possible that people observing an HTTPS connection being established wouldn't know how to decrypt it?

I've often heard it said that if you're logging in to a website - a bank, GMail, whatever - via HTTPS, that the information you transmit is safe from snooping by 3rd parties. I've always been a little ...
291
votes
3answers
298k views

What's the difference between SSL, TLS, and HTTPS?

I get confused with the terms in this area. What is SSL, TLS, and HTTPS? What are the differences between them?
243
votes
3answers
56k views

CRIME - How to beat the BEAST successor?

With the advent of CRIME, BEAST's successor, what possible protection is available for an individual and/or system owner in order to protect themselves and their users against this new attack on TLS?
231
votes
20answers
44k views

How can someone go off-web, and anonymise themselves after a life online?

With data mining tools like Maltego and other correlation tools for large data sets, if we conduct any transactions online assume that these can all be collated to build a good picture of what we do, ...
228
votes
11answers
34k views

How to explain Heartbleed without technical terms?

Most of my friends who are not experienced in computers want to know what Heartbleed is and how it works. How would one explain Heartbleed to someone without a technical background?
227
votes
16answers
50k views

SQL injection is 17 years old. Why is it still around?

I'm no techie and would like your expertise in understanding this. I recently read a detailed article on SQLi for a research paper. It strikes me as odd. Why do so many data breaches still happen ...
219
votes
7answers
44k 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'...
217
votes
4answers
97k views

SSL3 “POODLE” Vulnerability

Canonical question regarding the recently disclosed padding oracle vulnerability in SSL v3. Other identical or significantly similar questions should be closed as a duplicate of this one. What is ...
213
votes
5answers
14k views

Is the save button delay in a Firefox download dialog a security feature? What does it protect?

When I click to download a file through Firefox, a dialog window appears asking me whether I want to save the file somewhere or open it immediately once downloaded. The OK button in the dialog ...
206
votes
17answers
18k 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 ...
206
votes
15answers
10k views

Tracing the location of a mobile IP from an email

I'm a TV scriptwriter - and not hugely tech-savvy, so please bear with me... If the police have an email, sent by a suspect over a 3G or 4G network, could they use the IP address (since they know ...
202
votes
1answer
72k views

How exactly does the OpenSSL TLS heartbeat (Heartbleed) exploit work?

I've been hearing more about the OpenSSL Heartbleed attack, which exploits some flaw in the heartbeat step of TLS. If you haven't heard of it, it allows people to: Steal OpenSSL private keys Steal ...
199
votes
5answers
124k views

What is a specific example of how the Shellshock Bash bug could be exploited?

I read some articles (article1, article2, article3, article4) about the Shellshock Bash bug (CVE-2014-6271 reported Sep 24, 2014) and have a general idea of what the vulnerability is and how it could ...
193
votes
7answers
40k views

Why would you not permit Q or Z in passwords?

Jetblue's password requirements specify that, among other stringent requirements: Cannot contain a Q or Z I can't fathom a logical reason for this, unless it were say, extremely common for the ...
192
votes
14answers
30k views

My college is forcing me to install their SSL certificate. How to protect my privacy?

My college administration is forcing us to install Cyberoam Firewall SSL certificate so that they can view all the encrypted traffic to "improve our security". If I don't install the certificate than ...
182
votes
7answers
24k views

How do certification authorities store their private root keys?

Knowledge of a CA private key would allow MitM attackers to transparently supplant any certificates signed by that private key. It would also allow cyber criminals to start forging their own trusted ...
181
votes
21answers
23k views

How can I explain to non-techie friends that “cryptography is good”?

After that case in which Brazilian government arrested a Facebook VP due to end-to-end encryption and no server storage of messages on WhatsApp to prove connection with a drug case, it's become pretty ...
180
votes
8answers
82k views

Why not use larger cipher keys?

RSA Security commonly uses keys of sizes 1024-bit, 2048-bit or even 3072-bit. And most Symmetric algorithms only between 112-bit and 256-bit. I do realize that the current keys are secure enough for ...
175
votes
8answers
39k views

Why are salted hashes more secure for password storage?

I know there are many discussions on salted hashes, and I understand that the purpose is to make it impossible to build a rainbow table of all possible hashes (generally up to 7 characters). My ...
174
votes
3answers
30k views

Don't understand how my mum's Gmail account was hacked

My mum (on Gmail, using Chrome) received an email from a friend's Hotmail address. She opened the email (very obviously a phishing email) and clicked a link in it. This opened a webpage with loads of ...
173
votes
3answers
13k views

What is the purpose of “gibberish” comments posted to my blog?

Fairly frequently, the contact form on my blog gets comments that look similar to this (each field represents a text box users can enter into the HTML form on the blog): Name: 'ceguvzori' Email: ...
171
votes
4answers
42k views

How does Windows 10 allow Microsoft to spy on you?

Windows 10 is perhaps the most Internet-connected and cloud-centric operating system released by Microsoft to date. This, of course, has caused many users to be concerned about how the OS respects ...
168
votes
8answers
28k views

Why can't the FBI read the key embedded in the iPhone's secure chip/ROM directly from hardware (silicon)?

As far as I understand, the 4 digit passcode is combined (in some fashion) with a key stored in secure read only memory (e.g. secure enclave chip or similar), where it is directly embedded into ...
164
votes
10answers
37k views

Is “the oft-cited XKCD scheme […] no longer good advice”?

I was stumbling around and happened onto this essay by Bruce Schneier claiming that the XKCD password scheme was effectively dead. Modern password crackers combine different words from their ...
161
votes
12answers
42k views

How is an ATM secure?

I'm curious why an ATM computer is considered secure. The general adage of "If an attacker has physical access to my machine, all bets are off," seems to not apply in this circumstance (since ...
159
votes
8answers
76k 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?
158
votes
5answers
45k views

Why are chips safer than magnetic stripes?

After the recent Target hack there has been talk about moving from credit cards with magnetic stripes to cards with a chip. In what ways are chips safer than stripes?
158
votes
6answers
18k views

Apple's open letter - they can't or won't backdoor iOS?

Apple released an open letter to the public outlining their reasons for not complying with the FBI's demands to modify the iPhone's security mechanism. Here's a summary: The FBI has an iPhone in ...
157
votes
18answers
17k views

What is a good analogy to explain to a layman why passwords should be hashed?

Note: This is not an actual situation I'm currently in. Assume your boss is one of those old-fashioned computer-illiterate managers and wants to store the passwords in plaintext to simplify ...
157
votes
2answers
21k views

What is DROWN and how does it work?

There is a new recent attack "on TLS" named "DROWN". I understand that it appears to use bad SSLv2 requests to recover static (certificate) keys. My question is: How? How can you recover static ...
156
votes
11answers
59k views

Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it?

Why can't a password hash be reverse engineered? I've looked into this ages ago and have read lots on it, but I can't find the explanation of why it can't be done. An example will make it easier to ...
151
votes
4answers
18k views

Is there anything preventing the NSA from becoming a root CA?

There are now tons of Certification Authorities (CAs) that are trusted by default in major OS's, many of which are unrecognizable without online lookup or reference. While there have been attempts ...
151
votes
2answers
94k views

What is the difference between https://google.com and https://encrypted.google.com?

Is it there any difference between the encrypted Google search (at https://encrypted.google.com) and the ordinary HTTPS Google search (at https://google.com)? In terms of security what were the ...
148
votes
5answers
22k views

Does Facebook store plain-text passwords?

I was about to reset my Facebook password and got this error: Your new password is too similar to your current password. Please try another password. I assumed that Facebook stores only password ...
147
votes
8answers
26k views

What are the implications of NSA surveillance on the average internet user?

It would appear as though the tinfoil hat-wearing were vindicated today, as news broke of the true scale of the U.S. government's surveillance of its citizens' online activities, conducted primarily ...
147
votes
5answers
103k views

What is certificate pinning?

I'm superficially familiar with SSL and what certs do. Recently I saw some discussion on cert pinning but there wasn't a definition. A DDG search didn't turn up anything useful. What is certificate ...
146
votes
4answers
90k views

What exactly does it mean when Chrome reports 'no certificate transparency information was supplied by the server?'

When visiting Gmail in Chrome, if I click on the lock icon in the address bar and go to the connection tab, I receive a message 'no certificate transparency information was supplied by the server' (...

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