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Questions tagged [tls]

SSL (Secure Sockets Layer) and/or TLS (Transport Layer Security)

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1288 votes
3 answers

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. ...
Polynomial's user avatar
  • 135k
584 votes
3 answers

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?
jrdioko's user avatar
  • 13.2k
445 votes
9 answers

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?
Morten's user avatar
  • 4,603
420 votes
14 answers

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 ...
Joshua Carmody's user avatar
372 votes
6 answers

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 ...
Son of the Wai-Pan's user avatar
310 votes
3 answers

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?
Kyle Rosendo's user avatar
  • 4,035
250 votes
4 answers

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 the ...
tylerl's user avatar
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245 votes
14 answers

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 ...
svetaketu's user avatar
  • 2,171
243 votes
5 answers

What is the difference between and

Is it there any difference between the encrypted Google search (at and the ordinary HTTPS Google search (at In terms of security what were the ...
BlueBerry - Vignesh4303's user avatar
234 votes
8 answers

What is the difference between SSL vs SSH? Which is more secure?

What is the difference between SSH and SSL? Which one is more secure, if you can compare them together? Which has more potential vulnerabilities?
Am1rr3zA's user avatar
  • 3,093
219 votes
7 answers

Does https prevent man in the middle attacks by proxy server?

There is a desktop client A connecting to website W in a https connection A --> W Somehow between A and W, there is a proxy G. A --> G --> W In this case, will G be able to get the ...
jojo's user avatar
  • 2,301
203 votes
7 answers

How do mobile carriers know video resolution over HTTPS connections?

Verizon is modifying their "unlimited" data plans. Customers in the USA can stream video at 480p -or- pay to unlock higher resolutions (both 720p and +1080p). They are not the only mobile carrier to ...
raithyn's user avatar
  • 1,843
172 votes
11 answers

Is visiting HTTPS websites on a public hotspot secure?

It's often said that HTTPS SSL/TLS connections are encrypted and said to be secure because the communication between the server and me is encrypted (also provides server authentication) so if someone ...
Calmarius's user avatar
  • 1,975
170 votes
4 answers

Difference between .pfx and .cert certificates

What is the difference between .pfx and .cert certificate files? Do we distribute .pfx or .cert for client authentication?
Xsecure123's user avatar
  • 1,823
170 votes
13 answers

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 ...
johndodo's user avatar
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166 votes
10 answers

How do I run proper HTTPS on an Internal Network?

This question has been asked several times, I'll link a few:
alficles's user avatar
  • 1,761
160 votes
2 answers

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 ...
SEJPM's user avatar
  • 9,780
153 votes
4 answers

Which security measures make sense for a static web site?

I have a static web site. Users cannot log in or perform any other actions. Which of the common HTTP security measures make sense for my site? Do I need any of these? HTTPS Strict transport security ...
Sjoerd's user avatar
  • 30.9k
144 votes
14 answers

Is there any technical security reason not to buy the cheapest SSL certificate you can find?

While shopping for a basic SSL cert for my blog, I found that many of the more well-known Certificate Authorities have an entry-level certificate (with less stringent validation of the purchaser's ...
Luke Sheppard's user avatar
143 votes
3 answers

What's the purpose of DH Parameters?

For a Diffie–Hellman (D-H) key exchange (TLS) the server generates a prime p and a generator g, which is a primitive root modulo p. When setting up a webserver with SSL/TLS (e.g. nginx) one can use a ...
Ben Richard's user avatar
  • 3,686
134 votes
4 answers

Is it safe to include an API key in a request's URL?

Lately I've seen plenty of APIs designed like this: curl "" Isn't it elementary that passing an API key in a query string as a part of ...
Incerteza's user avatar
  • 2,247
131 votes
7 answers

Let's Encrypt for intranet websites?

Many companies have intranet websites that are not reachable via the internet. Usually they just use a self-signed certificate, which causes a bad habit for the users since they get used to just ...
LoukiosValentine79's user avatar
130 votes
5 answers

How do I use "openssl s_client" to test for (absence of) SSLv3 support?

In order to mitigate the "Poodle" vulnerability, I'd like to disable SSLv3 support in my (in this case, TLS, rather than HTTPS) server. How can I use openssl s_client to verify that I've done this?
Roger Lipscombe's user avatar
130 votes
5 answers

Should SSL be terminated at a load balancer?

When hosting a cluster of web application servers it’s common to have a reverse proxy (HAProxy, Nginx, F5, etc.) in between the cluster and the public internet to load balance traffic among app ...
Matt Goforth's user avatar
  • 1,303
127 votes
2 answers

How is the Heartbleed exploit even possible?

I have read about the Heartbleed OpenSSL vulnerability and understand the concept. However what I don't understand is the part where we pass 64k as the length and the server returns 64kb of random ...
Talha Sayed's user avatar
  • 1,001
122 votes
8 answers

Attacking an office printer?

I did an nmap scan on an advanced office printer that has a domain name and is accessible from outside the corporate network. Surprisingly I found many open ports like http:80, https:443, and svrloc:...
hsnm's user avatar
  • 1,291
118 votes
4 answers

What certificates are needed for multi-level subdomains?

I'm working on a web site with a several levels of subdomains. I need to secure all of them with SSL, and I'm trying to determine the correct certificate strategy. Here's what I need to secure: foo....
Nathan Long's user avatar
  • 2,764
116 votes
18 answers

Does an established HTTPS connection mean a line is really secure?

From the view of somebody offering a web application, when somebody connects with TLS (https) to our service and submits the correct authentication data, is it safe to transmit all sensitive data over ...
Peter Smit's user avatar
  • 2,749
115 votes
6 answers

I can't access websites that use HTTPS, instead getting the message "your connection is not private"!

I found myself suddenly unable to access websites that use HTTPS, so I contacted my service provider, and they asked me to install a certificate in the Trusted Root Certificate Authorities store. But ...
Tarek's user avatar
  • 1,063
114 votes
11 answers

Should I change the private key when renewing a certificate?

My security department insists that I (the system administrator) make a new private key when I want a SSL certificate renewed for our web servers. They claim it's best practice, but my googling ...
Commander Keen's user avatar
112 votes
9 answers

Is it safe to send clear usernames/passwords on a https connection to authenticate users?

I'm setting up a home HTTP server which can send and receive JSON data to/from different clients (Android and iPhone apps). I'd like to allow access only to certain users and I'm considering using a ...
Emiliano's user avatar
  • 1,223
110 votes
6 answers

Why should I offer HTTP in addition to HTTPS?

I am setting up a new webserver. In addition to TLS/HTTPS, I'm considering implementing Strict-Transport-Security and other HTTPS-enforcement mechanisms. These all seem to be based on the assumption ...
lofidevops's user avatar
  • 3,610
107 votes
4 answers

Now that it is 2015, what SSL/TLS cipher suites should be used in a high security HTTPS environment?

It has become quite difficult to configure an HTTPS service that maintains "the ideal transport layer". How should an HTTPS service be configured to permit some reasonable level of compatibility while ...
rook's user avatar
  • 47.2k
105 votes
5 answers

How does SSLstrip work?

I've been reading up on SSLstrip and I'm not 100% sure on my understanding of how it works. A lot of documentation seems to indicate that it simply replaces occurrences of "https" with "http" in ...
Scott Helme's user avatar
  • 3,238
103 votes
4 answers

What is ECDHE-RSA?

What is the difference between ECDHE-RSA and DHE-RSA? I know that DHE-RSA is (in one sentence) Diffie Hellman signed using RSA keys. Where DH is used for forward secrecy and RSA guards against MITM, ...
Hubert Kario's user avatar
  • 3,808
101 votes
5 answers

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 ...
Lernkurve's user avatar
  • 1,144
101 votes
4 answers

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 ...
Brandon Yarbrough's user avatar
100 votes
5 answers

Are there any downsides to using Let's Encrypt for a website's SSL certificates?

On the advantages side, I see several benefits to using the Let's Encrypt service (e.g., the service is free, easy to setup, and easy to maintain). I'm wondering what, if any, are the disadvantages to ...
Dolan Antenucci's user avatar
97 votes
9 answers

Can my company see what HTTPS sites I went to?

At work my company uses internet monitoring software (Websense). I know if I visit a https ssl-encrypted site (such as they can't see what I'm doing on the site since all ...
IAmARegisteredUser's user avatar
97 votes
10 answers

Why do we not trust an SSL certificate that expired recently?

Every SSL certificate has an expiration date. Now suppose some site's certificate expired an hour ago or a day ago. All the software by default will either just refuse to connect to the site or issue ...
sharptooth's user avatar
  • 2,241
95 votes
15 answers

Why would someone "double encrypt"?

If I have a website or mobile app, that speaks to the server through a secured SSL/TLS connection (i.e. HTTPS), and also encrypt the messages sent and received in-between user and server on top of the ...
Lighty's user avatar
  • 2,388
94 votes
4 answers

SSL Certificate framework 101: How does the browser verify the validity of a given server certificate?

(I have a basic understanding of public/private key, hashing, digital signatures... I have been searching online & stack forums last couple days but cannot seem to find a satisfactory answer.) ...
SecurityNoob's user avatar
  • 1,051
92 votes
4 answers

How to determine if a browser is using an SSL or TLS connection?

I want to know whether my browser is using SSL or TLS connection if I see HTTPS. I want to know for IE, Firefox, Chrome and Safari. I want to know the protocol version.
zhtway's user avatar
  • 1,163
90 votes
12 answers

How feasible is it for a CA to be hacked? Which default trusted root certificates should I remove?

This question has been revised & clarified significantly since the original version. If we look at each trusted certificate in my Trusted Root store, how much should I trust them? What factors ...
makerofthings7's user avatar
89 votes
7 answers

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 ...
noob Mama's user avatar
  • 993
88 votes
4 answers

What prevents me from buying a SSL certificate for a domain I don't control?

Can I simply build a webserver, make its hostname "", create a CSR off that server, and send that to a Certificate Authority for signing? Let's say I pick the cheapest and dodgiest outfit I ...
Flamer's user avatar
  • 859
88 votes
2 answers

ssltest: Chain issues - Contains anchor

I've run ssltest on web application and it found "Chain issues - Contains anchor" (section "Additional Certificates (if supplied)") What does it mean? Should it be fixed? Can it be exploited?
Andrei Botalov's user avatar
87 votes
5 answers

Are all SSL Certificates equal?

After running a few tests from Qualsys' SSL Labs tool, I saw that there were quite significant rating differences between a GoDaddy and VeriSign certificate that I have tested against. Are all SSL ...
Kyle Rosendo's user avatar
  • 4,035
85 votes
5 answers

What layer is TLS?

TLS stands for "transport layer security". And the list of IP protocol numbers includes "TLSP" as "Transport Layer Security Protocol". These two things would leave me to believe that TLS is a ...
Andrew Spott's user avatar
  • 1,002
85 votes
4 answers

What is Logjam and how do I prevent it?

I heard there is a "new" TLS vulnerability named Logjam, what does it do and how do I prevent it?
Arperum's user avatar
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