Questions tagged [public-key-infrastructure]

A public-key infrastructure (PKI) is a set of hardware, software, people, policies, and procedures needed to create, manage, distribute, use, store, and revoke digital certificates. In cryptography, a PKI is an arrangement that binds public keys with respective user identities by means of a certificate authority (CA). There are three main categories of PKI: Web / SSL certs, corporate networks, and Government ID / ePassport.

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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. ...
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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 ...
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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 ...
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11answers
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Is it completely safe to publish an ssh public key? [duplicate]

I use a RSA key to log into remote servers with ssh. And I keep my dot files under version control in a publicly accessible place so that I can quickly setup new servers to work the way I like. ...
98
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7answers
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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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4answers
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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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1answer
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How are private keys kept private?

This may sound like a stupid question but seriously how are private keys kept private? If you're someone like Google you have some huge number of servers to which the public can establish secure ...
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10answers
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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 ...
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Should I revoke no longer used Let's Encrypt certificates before destroying them?

The Let's Encrypt documentation recommends that when a certificate’s corresponding private key is no longer safe, you should revoke the certificate. But should you do the same if there are no ...
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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 ...
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How to check if an SSH private key has passphrase or not?

Let's say I have access to the private portion of an RSA key-pair. How can I check if this key has associated passphrase or not?
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Can I add a password to an existing private key?

Say I have previously created a private/public key combination, and decided at the time to not protect the private key with a password. If I later decide to "beef up" security and use a password-...
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6answers
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How does PGP differ from S/MIME?

Is S/MIME an abstracted system for general MIME type encryption, whereas PGP is more for email? Why would I want to choose one over the other, or can I use both at the same time?
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Why is there no certificate error while visiting google.net although it presents a certificate issued to google.com?

The following output shows that google.net is presenting a certificate that has been issued to www.google.com. $ openssl s_client -connect google.net:443 < /dev/null > out.txt 2>&1; cat ...
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Why can't you work backwards with public key to decrypt a message?

As the title suggests, I am curious to know why you can't work backwards using a message, public key and encrypted message to work out how to decrypt the message! I don't understand how a message can ...
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Why aren't IMSI catchers rendered ineffective by standard MITM defenses?

There's been a lot of reporting in the past few years about law enforcement agencies using IMSI catchers (also known as Stingrays after a popular brand of them) to intercept cellular communications. ...
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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 ...
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How does the digital signature verification process work?

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 ...
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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?
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3answers
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Can I get a public key from an RSA private key?

As far as I remember you encrypt the message using public key and decrypt it using private key. My question is whether it is possible to get a public key from an RSA private key. For example if I have ...
52
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4answers
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Can I sign a single character message with the RSA private key?

If I sign a very short message (0 or 1) with my private key (and the receiving side verifies the signature using public key), is this less secure than to send the sufficiently long signed message?
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What's the common pragmatic strategy for managing key pairs?

I have a small number of different workstations (plus client devices like iPhone) that I use for to connecting to numerous servers using SSH. Originally when I learned about PKI, I created a single ...
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2answers
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4096 bit RSA encryption keys vs 2048

Where do 4096 bit RSA keys for SSL certs currently stand in terms of things like CA support, browser support, etc? In the overall scheme of things is the increased security worth the risk of 4096 bit ...
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5answers
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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 ?
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2answers
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Can I restrict a Certification Authority to signing certain domains only?

Is it possible to create a CA certificate (even unsigned), which is only allowed to sign certificates for specific limited domain(s), so that it can't be misused for other domains?
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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 ...
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4answers
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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 ...
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How to set up OpenSSH to use x509 PKI for authentication?

I do not mean simply putting the public RSA key of a x.509 certificate into ~/.ssh/authorized_keys - I'm looking for a way to set up a ssh such that x.509 certificates signed by a pre-defined CA will ...
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7answers
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How dangerous might be publishing a public key? [duplicate]

Maybe this question sounds obvious, but I wonder how dangerous might be publishing a public key for an asymmetric encryption system? I know public keys are meant for encrypting messages by anyone who'...
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2answers
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How does RSA encryption compare to PGP?

On this answer ck says RSA and PGP are different. What you are essentially asking is how do I run my petrol car on diesel? The answer is you can't. I would be interested in a more ...
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4answers
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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?
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Is there any security risk when a certificate authority is used more than all others?

According to NetTrack, Let's Encrypt is now used on more than 50% of domains (51.21% as of April 2018). I know Let's Encrypt helped a lot of people to get free certificates for their websites, so I ...
37
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3answers
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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 ...
36
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Why do PGP master keys only have a single subkey, and tie certification with signing by default?

After learning more about PGP subkeys and how to split apart the roles of (S)igning, (E)ncryption, (A)uthentication and (C)ertification, I discovered that in most cases(?) a default master key has a ...
36
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4answers
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how to import a private key in windows

Say I have an X.509 cert and a private key that corresponds to it. I can import X.509 certs easily enough into Windows but what about private keys? Is the only way I can do that by converting both ...
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9answers
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How does SSL/TLS PKI work?

We have lots of questions that address portions of SSL/TLS as it relates to PKI, but none of them seem to bring everything together. A canonical answer that we can point people to I think would be ...
34
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5answers
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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 ...
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1answer
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Can a CSR be created in OpenSSL with SHA2?

Can a CSR be created in OpenSSL with SHA2? If so, what would the command be and what does this tell the CA, if anything? If you could create a CSR using SHA2 would it "tell" the signing CA to use it ...
31
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3answers
73k views

How to get public key of a secure webpage?

How can I get the public key of a webpage like verisign , etc. using HTTPS protocol?
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9answers
11k views

Can a HTTPS connection be compromised because of a rogue DNS server

If I'm visiting (just a desktop PC, client side) a site that has a valid HTTPS cert/connection, that can it be compromised if I'm using a rogue DNS server (not deliberately, I'm concerned about an ...
29
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3answers
11k views

Why is it more secure to use intermediate CA certificates?

I've read that using Intermediate CA certificates is more secure because this way the Root CA is offline. So, if the Intermediate is compromised it does not impact the Root CA. What I understand is ...
29
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4answers
21k views

SSL root certificate optional?

I may have been under the wrong impression on how servers should be setup and what certificates actually get sent over during the server hello certificate message. I came across this today from ...
28
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5answers
9k views

When can I commit a Private Key to source control?

That is to say, in what cases does it make sense to commit an unencrypted keypair to internal source control like SVN or Git? Related question that discusses an encrypted private key: Is it bad ...
28
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6answers
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Shouldn't GPG key fetching use a secure connection?

If I run this for example: gpg --keyserver hkp://keyserver.ubuntu.com --recv-keys 0xFBB75451 then does the importing occur in a secure way? I mean does it go over only secured connections? (HKP?) ...
27
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Creating my own CA for an intranet

I need to create my own CA for an intranet and unfortunately it seems there's no good answer about this on Security.SE. There are many resources online about this, but all of them are different and ...
27
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1answer
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Which properties of a X.509 certificate should be critical and which not?

RFC5280's section 4.2 states Each extension in a certificate is designated as either critical or non-critical. A certificate-using system MUST reject the certificate if it encounters ...
27
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5answers
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How are Chrome and Firefox validating SSL Certificates?

How are Chrome and Firefox validating SSL Certificates? Are they requesting data from an SSL certification website, like GeoTrust, to validate the certificate received from the web server?
26
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2answers
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If you revoke a certificate authority's certificate, do all of the certificates it issued become invalid as well?

If you revoke a certificate authority's certificate, do all of the certificates it issued become invalid as well? What about for certificates issued by an authority beneath it? For example, if root ...
26
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2answers
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How does Authy's 2FA work, if it doesn't connect to the server?

I thought I knew how two-factor authentication works: I enter the password. Server generates a random number (token) and sends it to me via SMS. I enter this token. Server checks that the token I ...
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3answers
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Which SSH security is stronger? 2 Factor or Public key

For SSH authentication, which is more secure? 2 Factor Authentication using a USB token/Google Authenticator(time based) OR Public/private key with password Or could they be both used at the same ...

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