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33

This is an historically disputed point. In the validation algorithm from RFC 5280 (that supersedes RFC 2459, by the way), there is no requirement of validity range nesting. However, some historical implementations have insisted on it; see for instance the X.509 style guide of Peter Gutmann: Although this isn't specified in any standard, some software ...


14

Hmm, I agree that I would have expected to find this info in RFC 5280 4.1.2.5. Validity. (By the way, RFC 5280 obsoletes RFC 3280, which obsoletes RFC 2459, so you really shouldn't be looking at 2459 any more). That said, you can figure this one out logically (at least for a standard TLS-like setting): When an end-user validates a cert, they have to follow ...


8

Let's Encrypt can only issue certificates for valid DNS names. So if your intranet uses a made-up domain name like intranet.mycompany.local then it won't work. If you have a real DNS name like intranet.mycompany.com (even if it doesn't resolve externally to your intranet), then you can use Let's Encrypt to issue certificates for it. If the domain does ...


5

It would be a huge operational cost in environments that don't have automated certificate management in place, which, in reality is the vast majority of the operational environments in the world today. In fact, in most environment little to nothing is automated. We've just started seeing people dip their toes in those waters in the past few years, and most ...


4

One common attack method consistent with your symptoms is DNS Hijacking, which is any means that an attacker uses to convince your computer that your bank's web site, "www.mybank.com" is actually at an IP which is a server under their control instead of the IP under your bank's control. When you type this into any browser, it heads for the malicious server ...


4

If you parse the certificate using openssl x509 -text, you'll get: Certificate: Data: Version: 3 (0x2) Serial Number: 31:64:4e:0c:95:4d:02:eb:78:97:11:6f:62:ee:71:02 Signature Algorithm: ecdsa-with-SHA256 Issuer: C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO ECC Domain Validation Secure ...


4

There is no security impact to either stop or continue the handshake -- the security relies in the tests performed by the client, not the server. This is why the extension is called an indication. What matters is that the client duly verifies that the apparent server public key is really owned by the intended server. The SNI is a way for the client to convey ...


4

Certificate validation is done against the hostname given in the URL, which means you'll need a certificate for any hostname which you expect to be used inside a URL. Thus, if you want to use both www.a.com and www.b.com in the URL you need a certificate for each, even if they are the same host and if one redirects to the other. DNS settings like same IP ...


3

This is why Microsoft recommends to never remove expired code signing certs from CRLs. An alternative scenario: attacker signs their malware before cert expiry. If they can remain undiscovered past cert expiry, then the cert won't get added to the CRL even on discovery, and their malware will never get blocked. Thus the revocation status of code signing ...


3

In short: the intermediate certificates have to be sent within the TLS handshake (needs proper configuration of the server) and only the CA local at the client will be considered as trust anchors. In detail: ... see that it does not have the issuing ca (intermediate ca's public key), will it automatically download those intermediate cert (e.g. ...


3

You can have multiple valid certificates with the same subject but different keys active at the same time. A possible use with SAN certificates would be to use certificates with the same subject but different key for the different hostnames contained in the certificate. You could even use it for the same hostname (i.e. same hostname on multiple IP addresses) ...


2

Seems to be a Man In The Middle attack with DNS spoofing. I suggest to perform a ping from an online service like this and check the IP address of the site. Then type it into your browser URL bar and check if you get redirect to the false website.


2

First, you should read through the most famous question on this site: How does SSL/TLS work?, having a good understanding of TLS will clear up a lot of your questions. Answering your questions: a) When a browser visit my site ... will prompt the end-user (using the browser) whether he/she wanted to install those certs? No, visiting a site in a ...


2

If the facts you mention in the Background section are true - there is no other way of making it work. If a client application looks for specific signature you can't use your proxy. I think the best way you can handle it is to write a script that identify Lync servers, and add it to the exempt list.


2

So they hacked my router? I didn't even know that was possible, but now that I think about it, it is remotely accessible on the LAN and the username/password is the manufacturer default. Will a hard reset of the router and then changing the username/password be sufficient now? Download the newest firmware for your router to a computer. Scan for ...


2

In X509 the fields making a certificate unique is the combination of issuer and serial number. Only the serial number is not guaranteed to be unique since two CAs may use the same serial. This is the reason both are typically needed for revocation. In practice, if you only have one CA, the serial will be enough of course. But it's not generic. There should ...


2

I have never heard the term "retire" applied to certificates. Maybe it has a specific meaning within the context of your certificate management tool? A "revoked" certificate should be considered compromised and no longer trusted. My guess is that a "retired" certificate is no longer being managed by the CA, but there's no evidence of compromise, so the ...


2

I would think this might have to do with what flag is used to mark the cert when it is added to the revocation list. A cert added with reason 4(superseded) or reason 5(cessationOfOperation) are not being revoked because of some compromise or inherent flaw so could be considered to be "retired". There have been several types of certs(sha1 and MD5) that are ...


2

On this certificate of yours, it's important to know if you signed it with your own company's root certificate; or did you have a third party sign it? If it's signed by your private root certificate, they won't have a copy so they have no way of validating the connections to you are legitimate. If you give them a copy, they will then have a way to validate ...


2

Installing root certificates on a server causes that server to implicitly trust any future certificates signed by that root. By installing that root cert, you could then use self-generated certificates that are signed be the root that was installed. This adds a layer of security in that your root is not distributed for use by other servers/instances, and ...


2

For websites which dynamically generate subdomain (for example, if users can create their own subdomain for some service), installing a certificate for each new subdomain is far from ideal, because you need to verify the ownership of the domain for each domain, followed by the installing of the certificate for each domain (which typically also requires a ...


2

You can place wildcards into the Subject Alternative Name (SAN) field of a certificate, so it's entirely possible to wildcard multiple domains. There are many CAs that will issue this under a name like "multiple domain certificate".


2

[Note: In the first wording of the question, there appeared to be some pretty glaring conceptual problems, the re-wording fixed these. I am going to leave this answer here anyway in hopes that it's useful to somebody.] PKI Fundamentals I think we need to go back to basics on how Public Key Infrastructure and certificates work. I am going to shamelessly ...


1

A few ways. Option 1: A proxy server with authentication. Phone -> proxy (check auth like basic auth if using https proxy, if not https proxy then no real security gain) -> internal-web-server We use these in corporations. You set an automatic proxy file (pac) on your phone to route requests to your domain web page through the proxy and the rest ...


1

The two options you mention are almost correct: However, you can (and should) install self-signed certificates without them being Certificate Authority certificates. The difference between a self signed cert and a CA cert is that a CA certificate is a special self-signed certificate with its "basicConstraints" set to "CA:true" (usually with the critical ...


1

SFTP is a subsystem of the SSH protocol. The SSH protocol session comprises several "moments", the key-exchange (or KEX) being the first one. So your SFTP client will: connect to the SSH server perform the key exchange and instantiate session encryption (from this moment on, the session is secure) send an authentication request which only contains the ...


1

Properly validating a certificate is a really complex matter. As with many things in crypto, it's best to leave this validation to a library instead of trying to implement it yourself. Typically, you'd ask your library to perform all the hard work and then check for any additional properties you are interested in afterward. As for the details: First, you ...


1

And you should make a lot of checks about the cerificate genuinity, i.e. to avoid MitM or false-issued certificate by "so-called stolen" CA key. Take a look and star at Perspectives Project to have a full picture


1

Resolved. The site needed to add the intermediate cert to the PEM file. I was overlooking the trust chain view in the browser that showed it was fetching the intermediate cert, a step that wasn't performed in the other use cases. So to answer my questions: The effective trust chain was in fact visible by calling up the security details by clicking the ...


1

Once you have deployed a private key in a USB Dongle it is impossible to extract it. This is the main reason to use a USB Dongle, to ensure the key is always hardware protected. The only option is to generate a new private key and request a new certificate



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