A piece of data used in public key cryptography that contains identifying information (i.e. email address or web address), a hash of a public key, and a digital signature that authenticates the data in the certificate.

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412
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3answers
178k 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 ...
151
votes
7answers
13k 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 ...
62
votes
11answers
14k views

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 Certificat Authorities have an entry-level certificate (with less stringent validation of the purchaser's ...
59
votes
4answers
39k 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 ...
56
votes
7answers
40k 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 ...
56
votes
2answers
19k views

What exactly does it mean when Chrome reports a certificate 'does not have public audit records'?

When visiting Gmail in Chrome, if I click on the lock icon in the address bar and go to the connection tab, I received a message 'The identity of this website has been verified by Google Internet ...
55
votes
10answers
9k views

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 ...
49
votes
4answers
14k views

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 ...
45
votes
4answers
34k 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 ...
43
votes
12answers
5k views

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 ...
43
votes
1answer
3k views

Why does Windows Ship with Expired SSL Certificates?

I am cleaning up the certificate stores on my Windows machines, and considering which certificates I should keep, and which ones I should delete. Why does a fresh install of Windows Server 2012 R2 ...
40
votes
5answers
25k views

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 ...
36
votes
4answers
29k views

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: ...
29
votes
7answers
7k views

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 ...
27
votes
2answers
58k views

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?
27
votes
3answers
53k views

Understanding 2048 bit SSL and 256 bit encryption

On DigiCert's page, they advertise a 2048 bit SSL with a 256 bit encryption: http://www.digicert.com/256-bit-ssl-certificates.htm What exactly is the difference here and why are two encryption bits ...
27
votes
2answers
1k views

Why aren't infinite-depth wildcard certificates allowed?

As far as I can tell, an SSL certificate for *.example.com is good for foo.example.com and bar.example.com, but not foo.bar.example.com. Wildcards certificates cannot have *.*.example.com as their ...
26
votes
8answers
6k views

Is anybody using client browser certificates?

Client browser certificates seem to be a nice way to protect sites from intruders - it is impossible to guess and should be harder to steal. Of course, they do not solve all the problems, but they add ...
26
votes
3answers
2k views

Is there a security issue in using the same certificate for all a company's services?

We are a small startup. One of our products is a B2B web service, accessible through its https://service.example.com canonical URL. For testing purposes, that service also runs on different ...
26
votes
4answers
4k views

What alternatives are there to the existing Certificate Authority system for SSL?

Whilst the current CA system works very well for a lot of people, it does put a lot of power into individual CAs' hands, and makes a CA hack potentially devastating for customers and business. What ...
26
votes
3answers
2k views

What is an SSL certificate intended to prove, and how does it do it?

If I get an SSL certificate from a well-known provider, what does that prove about my site and how? Here's what I know: Assume Alice and Bob both have public and private keys If Alice encrypts ...
25
votes
5answers
11k views

Where to get an SSL certificate for personal website?

I would like to use https to login to my personal webpage (which is on shared hosting). So I went over to google and started searching for sollutions. Eventualy I found out that I need an SSL ...
24
votes
2answers
14k views

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?
24
votes
3answers
978 views

A Different Approach to PKI

After yet another failure of the public key infrastructure, I was thinking about how broken the whole thing is. This business of undeniably associating an identity with a public key, and all the work ...
24
votes
5answers
18k views

What ciphers should I use in my web server after I configure my SSL certificate?

There are many great questions that ask what is the best certificate to use for a website; but once the certificate is purchased, there is also the possibility to choose or edit the Cipher list. ...
23
votes
9answers
4k views

Can an HTTPS site be malicious or unsafe?

I know it's possible for a computer to be infected just by visiting a website. I also know that HTTPS websites are secure. To my understanding, "secure" here refers to "immune to MITM attacks", but ...
23
votes
1answer
2k views

Why would the BBC web site always ask for a personal certificate, and how do I avoid giving it away?

After installing a CAcert personal certificate, every time I land on the BBC weather site it asks me to identify myself with a certificate. Why would any non-malicious web site do that unless I've ...
22
votes
1answer
2k views

Why does Firefox not trust this US government SSL certificate?

Shouldn't this be a trusted certificate considering it's a wildcard SSL certificate? That is, shouldn't *.delaware.gov cover www.corp.delaware.gov?
22
votes
3answers
10k views

What are the risks of self signing a certificate for SSL

Let's say I sign a SSL certificate for myself, and I'm not using a certified CA. What are the risks and/or threats of doing it?
21
votes
4answers
82k views

How can I export my private key from a Java Keytool keystore?

I would like to export my private key from a Java Keytool keystore, so I can use it with openssl. How can I do that?
21
votes
2answers
2k views

Digital Certificate deployment: using two certs for each user?

At a large enterprise environment I have come across a deployment approach for Digital Certificates where each user is issued two (2) key pairs: One for signing documents, emails, etc. that is ...
20
votes
5answers
2k views

Are login “certificates” more secure than standard username + password authentication?

I just opened a new bank account which comes with internet banking. Unlike the others I have used so far, this one requires a personal certificate (a .p12 file stored on my computer) + password for ...
18
votes
3answers
7k views

What vulnerabilities could be caused by a wildcard SSL cert?

In a comment on this answer, AviD says: "There are numerous security issues with wildcard SSL certs." So, what are the problems? I understand that the same private key is being used in multiple ...
18
votes
1answer
9k views

What is the difference between Serial Number and Thumbprint?

I have problems to understand what the difference between the Serial Number of a certificate and its SHA1 Hash is. the MSDN says: Serial number A number that uniquely identifies the ...
17
votes
3answers
2k views

Is SHA1 weak for SSL?

I noticed that today after I scanned a site on the Qualys SSL Labs site that SSL ciphersuites which use SHA1 are now highlighted as being "Weak". It seems this has just happened; I scan sites pretty ...
17
votes
2answers
2k views

How can you prevent employees of your company from creating valid ssl certs? [duplicate]

When registering for an SSL cert, I was able to validate that I "owned" the domain I was creating the cert for by having a valid @domain.com email address. If I worked for a large company, say ...
17
votes
4answers
3k views

What is the potential impact of these SSL certificate validation vulnerabilities?

I just finished reading through this paper by Georgiev et al, which demonstrates a wide range of serious security flaws in SSL certificate validation in various non-browser software, libraries and ...
17
votes
2answers
821 views

Encryption and the “security time decay” of prior encrypted data

This question is on the assumption that any data once encrypted, may (eventually) be decrypted through Brute force (compute power/time) Exploits in the cryptography used Theft of private keys ...
17
votes
3answers
3k views

Why can SSL certificates not be free of charge?

I am a newbie in this field. I am confused with why SSL certificates cannot be free of charge. In my understanding the certificate is just a text file consisting of cryptic numbers installed on a ...
17
votes
1answer
97k views

How do I clear cached credentials from my Windows Profile?

Windows seems to be saving my credentials for a variety of applications (terminal servers, etc) and I'd like to purge this data. How can I backup and purge this data?
16
votes
3answers
25k views

Expired SSL Certificate Implications

What are the security implications of an expired SSL certificate? For example if an SSL certificate from a trusted CA has expired will the communication channel continue to remain secure?
16
votes
4answers
6k views

Are there technical disadvantages in using free ssl certificates?

Note this question is related, except this one is about free SSL certs. There are providers who are offering totally free entry-level SSL certs (like StartSSL). I was wondering if they are ...
16
votes
3answers
2k views

What happens when an Intermediate CA is revoked?

Currently I'm working on a certificate manager that allows our product to securely connect to remote webservices (over TLS/SSL). For security, we use Certificate Revocation List checking (or ...
15
votes
2answers
15k views

Chrome SSL Warning: “You cannot proceed because the website operator has requested heightened security for this domain. ”

I'm trying to go to the URL below, and Chrome warns me that the wildcard certificate is not valid for this domain. ...
15
votes
7answers
8k views

How do I check if a gmail/gtalk SSL certificate is valid?

Pidgin started prompting me to accept/reject new gtalk SSL certificate a few days ago and I am not able at the moment to tunnel the traffic to check if it would continue to happen or if it wouldn't ...
15
votes
1answer
3k views

REST specific security weaknesses

I need to start working with RESTfull Web Services. SOAP based web services have already so many standards to secure communication, establish trust etc. I am not aware of any for REST. What I would ...
15
votes
3answers
1k views

What are the risks of a Certificate Authority hack for 'the average user'?

Recently the DigiNotar CA was hacked, and rogue certificates were issued. Since they also issue certificates on behalf of the Dutch government, the government made a statement about it as well, ...
14
votes
4answers
1k views

Is my Company Tracking Me?

Every time I try to connect to a site through HTTPS from my office computer, there is a Certificate Error thrown 2-3 times before showing the login screen. Till now I use to ignore this and click ...
14
votes
4answers
15k views

how digital signature verification process works

I am not able to understand that how the digital signature is verified. I know that digital signature will be attached to the message and sent by sender to receiver. then receiver uses the public key ...
14
votes
5answers
3k views

Are self-signed certificates actually more secure than CA signed certificates now?

Are self-signed certificates actually more secure than CA signed certificates now? I ask this because recent leaks about the NSA spy programs and the secret FISA courts mean that the US government ...