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179

It is already done: It is the FPKI root CA, under explicit and full control of the US government. Windows already trusts it by default. Before you flip out and begin to delete root CA certificates, burn your computer's motherboard, or drink a gallon of vodka, think about what it means. It means that the US government could technically emit a fake ...


134

Serious certification authorities use heavy procedures. At the core, the CA key will be stored in a Hardware Security Module; but that's only part of the thing. The CA itself must be physically protected, which includes proactive and retrospective measures. Proactive measures are about preventing attacks from succeeding. For instance, the CA will be stored ...


64

When a certificate is expired, its revocation status is no longer published. That is, the certificate might have been revoked long ago, but it will no longer be included in the CRL. Certificate expiration date is the cut-off date for CRL inclusion. That's the official reason why certificates expire: to keep CRL size bounded. (The unofficial reason is to ...


56

A good question. The simplest answer is that having an expiration date ensures that you have an "audit" every so often. If there were no expiration date, and someone stopped using a certificate (and protecting the private key), no one would ever know. However, by having an expiration date you ensure that the user goes back to the company that sold them the ...


50

In essence, these certificates are necessary and required for backward compatibility with XP and Server 2003. If anything was signed with these certificates, even if they're expired now, your server needs the cert trusted in order to trust the thing that the cert signed. Source: http://support.microsoft.com/kb/293781 Some certificates that are listed in ...


45

For the purposes of this discussion there are only a couple differences between web signing certificates: Extended vs standard validation (green bar). Number of bits in a certificate request (1024/2048/4096). Certificate chain. It is easier to set up certificates with a shorter trust chain but there are inexpensive certs out there with a direct or ...


39

Disclaimer: This answer comes directly from the eHow article. No infringement intended. Domain Validation SSL Certificates Domain validated SSL certificates are used to establish a baseline level of trust with a website and prove that you are visiting the website you think you are visiting. These certificates are issued after the SSL issuer confirms ...


39

Update 5 The root problem (heh) with the CA model is that in general practice, any CA can issue certs for any domain, so you're vulnerable to the weakest link. As to who you can trust, I doubt that the list is very long at all, since the stakes are high and security is hard. I recommend Christopher Soghoian's post on the subject, which clarifies the ...


32

I like using StartCom for a free certificate. It's recognized in most major browsers and is better than using a self-signed certificate (No error prompts for users).


31

The NSA could and probably already has gone -- using a USA PATRIOT Act demand letter, or other similar legislative tool -- to all the major CAs in the United States (e.g. VeriSign, GeoTrust, etc.) and demanded that they remit their private root keys to "No Such Agency", "for purposes of 'national security'". Of course, all such requests must (per PATRIOT ...


27

On the physical side they first keep the root CA completely offline. Typically what happens is that they set up the root CA, make subordinates, then take the root CA completely offline and take the hard drives and HSMs (sometimes even the whole server) and essentially lock them in a safe. Next, they segment the network to keep those subordinate/issuing ...


25

As Matt Blaze once wrote, CAs protect you from anyone who they are unwilling to take money from. That should tell you something about where the CA's incentives lie, and some potential risks in the arrangement.


25

It is ultimately the responsibility of the client's user to check the validity of the certificate. As a service provider, apart from educating the user if you can, there is not much you can do on your side: you don't control which certificates are trusted by the user's browser and you can't know whether the users have verified they using SSL/TLS properly and ...


25

Last year, I made a bet with a friend that I can get a browser-trusted certificate with his domain name in order to launch a successful MiTM attack on his login form to steal his password. Long story short: I lost the bet; I wasn't able to convince any of the 16 CAs I contacted that I'm the legitimate owner of the domain. Even though I had an email account ...


21

At the byte level, X.509 is X.509 and there is no reason why the free SSL certificates would be any better or worse than the non-free -- the price is not written in the certificate. Any certificate provider can fumble the certificate generation, regardless of whether he gets paid for it or not. The hard part of a certificate is outside of it: it is in the ...


20

On a theoretical basis, an expired certificate is a certificate which must not be used any longer. This is made explicit in the the Internet X.509 Profile in the certificate validation algorithm (section 6.1.3, item a.2). In practice, this has two consequences: The key owner (the server) must keep its private key, well, private. Anybody who gets a copy of ...


19

The fingerprint, as displayed in the Fingerprints section when looking at a certificate with Firefox or the thumbprint in IE is the hash of the entire certificate in DER form. If your certificate is in PEM format, convert it to DER with OpenSSL: openssl x509 -in cert.crt -outform DER -out cert.cer Then, perform a SHA-1 hash on it (e.g. with sha1sum1): ...


18

Note: This is a (very very long) compendium of various recommendations and actions that Microsoft, NIST, and other well respected PKI and cryptography experts have said. If you see something that requires even the slightest revision, do let me know. Before I get into configuring the CA and its subs, it's good to know that even though MSFT's CryptoAPI ...


17

Using an SSL certificate for your websites primarily gets you two things: Identity proofing that your website is who it says it is Stream encryption of the data between the webserver and the client By doing what you propose, which is normally called self-signing, prevents you from relying on the identity proofing. By using a known trusted CA the client ...


16

The communication is still encrypted, but the trust mechanism is undermined. But usually the most important factor is that users will get ugly warning messages about the security of your site. Most won't make informed judgements about the integrity of the connection, they'll just go buy stuff elsewhere.


16

"Alternatives" depend on whether you want something which may work in the future, or something which works right now, with existing browsers. Right now, Web browsers expect that servers send X.509 certificates, and then they validate them against the set of root CA integrated in the browser (or operating system). This means that if you want something that ...


16

A CRL is an object which contains the list of serial numbers of certificates which have been revoked by a given CA. It is a signed object; the CRL issuer is usually the CA itself (with the same key) but this power can be delegated. An OCSP response is what an OCSP responder returns when it receives a request about the revocation status of a certificate. The ...


15

Yes, it can be issued. Luckily the common browsers do not accept wildcard certificates for TLDs. Chromium Source Code: DCHECK(reference_domain.starts_with(".")); // We required at least 3 components (i.e. 2 dots) as a basic protection // against too-broad wild-carding. // Also we don't attempt wildcard matching on a purely numerical hostname. ...


15

I'm afraid that the short answer to this question is that it's impossible to know, as far as I can see. There are a large number of default CA's installed in most common browsers and assessing how likely they are to be "trustworthy" in terms of giving out certificates to governmental or other organisation is difficult. If a CA became known as untrustworthy ...


14

DNSSec is normal DNS, but with signatures. It absolutely prevents DNS Spoofing; that's what it's for, and that's what it does. Registrars can still theoretically abuse their position because they're responsible for communicating your intentions to the root servers. This includes information about your DNSSec keys. This relationship will never change; if ...


14

Must/should I fetch all CRLs of the complete chain to check the certificates validity? Absolutely. A CA builds a CRL only for the certificates it issues. Status of the CA itself must be checked via the CRL of the issuing CA. Note: This is a recursive search. When writing code, or testing systems, remember that there can be more than one "generation" of ...


14

If there was a universal five-day grace period, nobody would notice the certificates' expiry until five days later, leaving you with an identical net effect to refusing an expired certificate immediately. It's the fact that SSL connections stop working that creates the pressure. I suspect it would be more productive for SSL client applications to warn ...


14

There is a subtle point here. In the envisioned situation, there is one (or several) rogue CA who may emit fake certificates for man-in-the-middle attacks. The vulnerability here is not about a server who uses a (genuine) certificate from that rogue CA; it is about the client potentially accepting a certificate from that CA. To protect yourself (as a client) ...


13

Well, technically, if the user cannot confirm the identity of the certificate owner, then the communication cannot be really secure, because a villain may impersonate the server; he may even relay the data to the right server transparently (that's the man-in-the-middle attack model). Making sure that you talk to the right server IS an integral part of the ...



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