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 ...

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353
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3answers
136k 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. ...
142
votes
7answers
11k 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 ...
54
votes
7answers
33k 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 ...
50
votes
10answers
7k 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 ...
43
votes
4answers
28k 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 ...
40
votes
4answers
28k 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 ...
34
votes
12answers
4k 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 ...
32
votes
7answers
4k views

How dangerous might be publishing a public key?

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 ...
25
votes
4answers
12k 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 ?
25
votes
4answers
14k views

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?
25
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 ...
24
votes
3answers
945 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 ...
23
votes
5answers
3k views

Why is Bruce Schneier recommending symmetric crypto over public key crypto

I just read the article written by Bruce Schneier, the crypto guru. In the article, he says : Prefer symmetric cryptography over public-key cryptography. But, he doesn't shed any light as to ...
21
votes
4answers
3k 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 ...
20
votes
3answers
2k 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 ...
19
votes
6answers
2k 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?) ...
17
votes
2answers
1k views

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 ...
17
votes
2answers
749 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
8k 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?
16
votes
2answers
5k views

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 ...
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
3answers
21k 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?
15
votes
4answers
2k views

Is there any reason someone wouldn't use a longer key?

Larger key sizes are said to be more difficult to bruteforce; is there any reason someone would then decide to instead use a smaller key? Is there any negative effect in using a larger key size, such ...
15
votes
4answers
4k 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 ...
14
votes
7answers
1k 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 [not with free will, so e.g.: I'm "attacked"] a rouge DNS ...
14
votes
4answers
11k 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
2answers
1k views

SSL fingerprint inconsistency: what does it mean?

I apologize if this is not the best place to ask my question on the stackexchange network, I couldn't figure out where to get enough attention and be relevant. Facebook provides a SSL host, it can be ...
13
votes
3answers
2k views

Computationally simple, lightweight replacement for SSL/TLS

Target hardware is a rather low-powered MCU (ARM Cortex-M3 @72MHz, with just about 64KB SRAM and 256KB flash), so walking the thin line here. My board does have ethernet, and I will eventually get ...
13
votes
1answer
1k 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
5answers
2k 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 ...
11
votes
4answers
1k views

What kinds of SSL certificates are usable for encryption?

I know that Verizon SSL certificates cost close to $600. There are couple of cheap alternatives, but I never really understood why Verizon does not offer such certificates. Look for RapidSSL at ...
11
votes
3answers
8k 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 ...
11
votes
3answers
377 views

How are private keys handled in an enterprise?

We would like to start using digital signatures and possibly encryption for e-mails in our company. My knowledge of public-key cryptography is entirely theoretical with no practical experience. In ...
11
votes
2answers
383 views

Is PGP secure against a rogue keyserver?

Imagine Eve taking over the keyserver both Alica and Bob are using. By replacing Alices and Bobs public keys with her own, she can do a man-in-the-middle attack decrypting messages and relaying them ...
11
votes
2answers
922 views

What does having an internal two-tier PKI protect against?

There are a lot of Best Practice documents that recommend having an offline Root CA and an Enterprise Subordinate CA that is signed by the root, for an internal Microsoft AD Certificate Services ...
10
votes
4answers
994 views

Why isn't OCSP required by default in browsers?

According to the following screenshot, taken from firefox-3.6.17-1.fc14.i686, Firefox has an option to fail closed when unable to connect to OCSP servers. Can someone please explain why this isn't ...
10
votes
2answers
1k views

Are there really functioning quantum computers?

I saw this video on youtube on quantum computing. It says that a company called dwavesys has already made commercially available quantum computer. I checked on the website and it exists. I thought ...
10
votes
3answers
1k 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 ...
10
votes
3answers
3k views

SSH password vs. key authentication

I've usually been told that public key authentication is strongly preferred over password authentication for SSH. However our previous admin was against public keys and only issued passwords and took ...
10
votes
2answers
1k views

Is it okay to widely share the RSA key fingerprint for a host?

When you ssh into a remote box for the first time or if the remote host's key fingerprint has changed (from what's stored in your known_hosts file) you get a warning and you are shown the fingerprint ...
10
votes
3answers
951 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 ...
10
votes
1answer
2k views

Renewing Microsoft Certificate Services Root Certificate

We currently have Microsoft Enterprise Certificate Server installed on a domain member machine which issues 1 year certificates to users for authenticating to VPN. We'd like to start issuing web ...
10
votes
4answers
8k 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?
9
votes
6answers
2k views

Should I hash a password if it is randomly generated

The best practice is we should hash a user password using algorithms such as bcrpyt to protect the user, however, given the following conditions, is hashing in the backend still matters? the ...
9
votes
3answers
2k views

How does an SSL server prove its identity?

This document says that a challenge response authentication proves the servers identity. But is a man in the middle attack still possible if the client does not verify domain name ? Please help me ...
9
votes
7answers
451 views

Authencity of information displayed on an untrusted device

Suppose I have a (bluetooth/usb) device which needs to displays information on an external pc/phone. Is there a simple and effective method to garantuee that the information displayed hasn't been ...
9
votes
2answers
4k 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
1answer
4k 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 ...
9
votes
2answers
379 views

PKI solution vendor selection

What would you look for in a (X.509-) PKI solution, and why would you look for that, given the following constraints: Available programming/sw-engineering know how is limited (ie, "OpenSSL with a ...
8
votes
3answers
2k views

Certificate authorities for a PKI

Some people think the certificate authorities for a PKI should be the government, but others think certificate authorities should be private entities, such as banks, corporations, or schools. What are ...