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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663
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3answers
342k 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 ...
134
votes
5answers
94k 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 ...
63
votes
12answers
8k 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 ...
17
votes
9answers
6k 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 ...
73
votes
10answers
20k 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 ...
18
votes
4answers
15k 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 ...
179
votes
7answers
23k 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 ...
70
votes
4answers
58k 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 ...
29
votes
4answers
24k 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 ?
21
votes
8answers
4k 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 ...
26
votes
4answers
35k 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 ...
31
votes
3answers
3k 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 ...
35
votes
3answers
23k 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?
22
votes
6answers
3k 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?) ...
12
votes
3answers
3k 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 ...
68
votes
7answers
72k 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 ...
6
votes
4answers
530 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 ...
5
votes
4answers
385 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 ...
1
vote
2answers
903 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 ...
22
votes
5answers
5k 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 ...
16
votes
5answers
2k 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 ...
9
votes
8answers
5k 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 ...
7
votes
4answers
30k 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 ...
7
votes
2answers
10k views

Certificate Chain checking

I have a very specific question. A client verifies a server by taking the certificate and checking specific values and that the digital signature of the intermediate CA is correct (according to the ...
5
votes
2answers
6k views

Extensions for SSL server certificate

I have some question about the X.509 v3 extensions. What extensions should appear in a proper certificate for a SSL server ?
16
votes
2answers
1k 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 ...
14
votes
2answers
2k 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 ...
10
votes
1answer
14k views

Reset Windows trusted certificates store to its default

Over the time I have installed several additional trusted CA certificates to Windows trust store, sometimes because an app pushed me to do so, some other times for development and testing. Is there ...
8
votes
2answers
510 views

Is there a way to negotiate a secret between 2 parties with no prior knowledge?

Is there a way for 2 parties to negotiate a shared secret (for example, a session key) without having a pre-shared knowledge? SSL does this by using asymmetric encryption. Is there any other way to ...
1
vote
1answer
99 views

Is it complicated to deploy my own CA?

We want to implement a free solution to sign digitally internal documents. No legal value of this sign are requested. We want to consider to deploy an internal CA. Why is it always said that keeping ...
6
votes
1answer
432 views

How long do keys stay on keyservers?

Do GPG/PGP keyservers "garbage collect" old keys which have expired, been revoked, or simply haven't been updated in a decade? Or does the server (theoretically) keep every key it has ever seen from ...
0
votes
3answers
197 views

Is it ok to send user's private key away, even if protected with a SSL channel?

I'm developing a webserver that performs digital signatures of (xml, pdf and office) documents and then validates those signatures. My idea is: an user puts its SmartCard and through a PIN, he gets ...
33
votes
4answers
4k 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 ...
18
votes
3answers
5k 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 ...
8
votes
1answer
3k views

How does adding a random serial number improve a certificates' 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, ...
28
votes
4answers
40k 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
2answers
2k 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
1answer
798 views

How secure is “Let's Encrypt”?

I just configured and installed a free SSL certificate from Let's Encrypt. It's great, and very easy to set up. However in this post-Snowden era, I was wondering how secure this really is. For ...
9
votes
2answers
386 views

I want trusted SMIME certificates for 3rd parties. Is this a reasonable configuration?

I want to send out SMIME certificates with my emails, and want to deploy the following PKI Root01 (All EKU, All Constrants, No Restrictions) PolicyInt01 (Internal applications, not trusted by 3rd ...
10
votes
3answers
5k 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 ...
3
votes
4answers
5k 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 ...
12
votes
4answers
2k 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 ...
7
votes
10answers
7k views

How can I share files with other individuals using the cloud in a secure way?

I would like to use a dropbox because it is easy and convenient. But I want to encrypt the files with the public key of the intended recipient, so he will be the only one who can access the data in ...
6
votes
2answers
208 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 ...
8
votes
1answer
2k views

Has the leaked D-Link windows signing key been revoked?

Recently news broke as to D-Link mistakenly publishing a private code-signing key as part of an open source framework. The D-Link key was leaked in late February, and expired on September 3, it ...
3
votes
2answers
369 views

Explicitly prohibit an intermediate CA certificate on OpenSSL

How do you explicitly not trust a particular certificate (especially, CA certificate) for OpenSSL? On NSS-based applications, one can install the cert with trustarg p: prohibited (explicitly ...
3
votes
1answer
2k views

What are the Netscape Cert Type attributes? Why/when are they needed?

What are the Netscape Cert Type attributes in a X.509 Certificate and how are they different with the X509v3 extensions? Example: There is the Client/Server Extended Key Usage (X.509) but there is ...
2
votes
3answers
1k 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 ...
8
votes
3answers
2k views

Is it safe to store a single symmetric key encrypted with several different RSA public keys?

For the field-based encryption of a database containing sensitive information, I was thinking of the following design: Every user has a smartcard used for client certificate login. After login the ...
5
votes
3answers
2k 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 ...