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.

Filter by
Sorted by
Tagged with
1220
votes
3answers
651k 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. ...
346
votes
6answers
304k 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 ...
89
votes
12answers
16k 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 ...
16
votes
4answers
5k views

If the public key can't be used for decrypting something encrypted by the private key, then how do digital signatures work?

I'm learning asymmetric encryption in the use case of ssl/tls protocol. I can understand that the public key (like a padlock) can encrypt (lock) something and only the private key can decrypt (open)...
38
votes
9answers
36k views

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 ...
32
votes
9answers
12k 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 ...
255
votes
7answers
47k 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 ...
46
votes
5answers
49k views

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 ?
92
votes
10answers
35k 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 ...
63
votes
4answers
101k views

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 ...
27
votes
4answers
24k views

Checklist on building an Offline Root & Intermediate Certificate Authority (CA)

Microsoft allows a CA to use Cryptography Next Generation (CNG) and advises of incompatibility issues for clients that do not support this suite. Here is an image of the default cryptography settings ...
7
votes
2answers
898 views

Could a stolen certificate show as trusted?

I have recently started learning about PKI and have the following question/s. As far as I know a signed certificate contains the domain name of the server that the certificate will be placed upon. ...
56
votes
2answers
53k 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?
39
votes
3answers
6k 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 ...
46
votes
5answers
21k 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 ...
7
votes
3answers
5k views

Digital Signature and Verification?

AFAIK , When Alice wants to write a message to Bob -- she uses Bob's public key and encrypt the message - and then Bob - using his private key - use to decrypt it. So public key is used to decrypt ...
98
votes
4answers
115k 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 ...
49
votes
2answers
12k views

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?
29
votes
2answers
36k views

SSL certificates and cipher suites correspondence

I have been learning about the SSL/TLS protocol (from https://tools.ietf.org/html/rfc5246) and have a few conceptual questions about the protocol. The client and server exchange "hello" messages ...
18
votes
5answers
8k views

Multiple CAs signing a single Cert/CSR?

Just saw this suggested on Slashdot So I've seen quite a few people wanting a switch to self-signed certs (who IMO mostly don't understand what making that secure actually involves), and an idea to ...
100
votes
7answers
141k 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 ...
7
votes
2answers
5k views

Can a RootCA be revoked?

I have created a New Trusted certification authority which issues certificate to the end entity and the end entity will use this certificate as trusted one for all their PKI operations. Some how the ...
28
votes
6answers
7k views

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?) ...
15
votes
1answer
6k views

Manually walking through the signature validation of a certificate

Since I am not too familiar with the Web of Trust and Public Key-Infrastructure I decided to learn about it by following the signing chain of a X.509 certificate issued to CN=*wikipedia.org (Serial ...
12
votes
4answers
15k views

When should I use symmetric encryption instead of RSA?

I'm currently using GPG RSA keys to encrypt binary files. Many people recommend using symmetric keys to encrypt large files, and then encrypt the symmetric key with a public key. At what file size ...
30
votes
5answers
16k views

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 ...
42
votes
4answers
39k views

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 ...
19
votes
8answers
20k views

Is Spoofing a CA signed certificate possible?

I had never thought about this situation before, I may be completely wrong but I am going to have to clarify it anyway. When a communication starts with a server, during the client handshake, the ...
37
votes
4answers
60k 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?
10
votes
4answers
37k views

SSL Client Certificate authentication

Is it possible to make a program which uses client certificate authentication with only public and private key (I have not generated any certificate, I have only public and private key). Simply, I ...
31
votes
5answers
23k 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 ...
22
votes
3answers
54k views

How to reset Windows trusted certificates store to its default [closed]

Over time I have installed several additional trusted CA certificates to Windows trust store, sometimes because an app pushed me to do so, other times for reasons of development and testing. Is ...
19
votes
2answers
2k 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 Most ...
16
votes
3answers
4k views

Difference between Certificate Authorities

I've been wondering for a long time about is. There are many certificate authorities having different types of certificates. But even certificates of the same security level cost a lot more with one ...
8
votes
4answers
772 views

What fields in a suspicious certificate should I look at?

Looking at a certificate for a web-site (in Windows/Google Chrome) I see it lists the following fields Version Serial number Signature algorithm Issuer Valid from Valid to Subject Public Key Basic ...
6
votes
2answers
451 views

Using a verified certificate to sign others

This relates to PKI and certificates generally but websites more specifically. Could you get a verified certificate from a CA that is signed and fine for use, and then use it to sign your own ...
2
votes
2answers
4k views

ECDSA ciphers and forward secrecy question about key exchange

I have heard that with forward secrecy that the ECDSA ciphers generate different keys for "each session" because they are not dependent on the private key of the server. My question is how is "each ...
84
votes
4answers
152k views

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-...
68
votes
7answers
49k views

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 ...
49
votes
4answers
13k views

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 ...
34
votes
5answers
8k 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 ...
29
votes
5answers
47k views

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?
29
votes
3answers
12k 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 ...
14
votes
1answer
6k views

How does adding a random serial number improve a certificate's security?

This article says: "Finding collisions is a tricky process, since it requires you to muck with the bits of the public key embedded in the certificate (see this paper for more details). Also, ...
20
votes
2answers
5k views

How would I implement “Broadcast Encryption”?

I have a stream that I want to encrypt for broadcast to 10,000 subscribers. I know I should encrypt this data using a symmetric key; and also intend that this symmetric key will be rotated every 30 ...
12
votes
2answers
10k views

SSL Certificate revocation check

In the SSL protocol I don't see where the certificate is checked for revocation status. https://developer.mozilla.org/en/Introduction_to_SSL Is the Certificate Revocation and Status Checking not ...
9
votes
3answers
10k views

What is the web of trust?

I'm studying network and system security and I came across the phrase "web of trust". From Wikipedia: In cryptography, a web of trust is a concept used in PGP, GnuPG, and other OpenPGP-compatible ...
9
votes
1answer
19k views

Why is a CA certificate required for EAP-TLS clients?

When setting up clients with WPA2 EAP-TLS, most clients (ie: my phone, my computer) require both a client public/private keypair (for obvious reasons) and a certificate authority certificate. It's ...
6
votes
3answers
5k views

What stops a hacker from installing its own CA certificate?

Taking a look at this (now rather old) article about the generated rogue DigiNotar certificates, it states the following: ...Such is the case with that small company in the Netherlands, DigiNotar....
1
vote
2answers
5k views

Understanding Certificate Pinning [duplicate]

I am attempting to implement certificate pinning across a suite of mobile apps. I have been reading a lot about the different strategies (pinning to the CA/intermediate, pinning to a leaf cert, ...

1
2 3 4 5 6