Questions tagged [x.509]

X.509 is a standard for a public key infrastructure used for authentication and access control. X.509 specifies standard formats for certificates, revocation lists, attribute certificates, and path validation.

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74
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2answers
93k views

What is the difference between serial number and thumbprint?

I have problems to understand what is the difference between the serial number of a certificate and its SHA1 hash. The MSDN says: Serial number A number that uniquely identifies the ...
70
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1answer
10k views

Why is there no certificate error while visiting google.net although it presents a certificate issued to google.com?

The following output shows that google.net is presenting a certificate that has been issued to www.google.com. $ openssl s_client -connect google.net:443 < /dev/null > out.txt 2>&1; cat ...
54
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2answers
94k views

What's the difference between X.509 and PKCS#7 Certificate?

Am I correct calling file with .p7b file extension saved as 'Cryptographic Message Syntax Standard - PKCS#7 Certificates (.P7B)' in Windows - a 'PKCS#7 certificate'? Or is it better called 'X.509 ...
47
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2answers
54k views

What is the difference between SSL and X.509 Certificates?

I used openssl to create a X.509 certificate but I don't quite understand the relationship between a X.509 and a SSL certificate. Are they the same? Is a SSL certificate just a X.509 certificate that ...
41
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2answers
16k views

Determine if private key belongs to certificate?

Given a certificate¹ and a private key file², how can I determine if the public key on the certificate matches the private key? My initial thought was to simply encrypt some text with the public key ...
38
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3answers
31k 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 ...
36
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2answers
5k views

Can a SSL certificate have longer validity period than its parent in X.509 chain?

When a X.509 certificate chain is composed of X1, X2 ... Xn and Xn is root CA, Can a certificate in lower level have longer validity period than its parents? I think that lower level should be proper ...
34
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7answers
7k views

Could governments and banks become CAs?

When you apply for a passport, driver's license, home mortgage, bank account, credit card, etc., the issuing organization must verify your identity. In the course of doing so, would it be feasible for ...
27
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1answer
28k views

Which key usages are required by each key exchange method?

I'm only really concerned with RSA keys, so the exchange methods are RSA (generate a key, encrypt it, and send it over) and [EC]DHE_RSA (generate an ephemeral [EC]DH key, sign it, and use it for key ...
26
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2answers
4k views

If you revoke a certificate authority's certificate, do all of the certificates it issued become invalid as well?

If you revoke a certificate authority's certificate, do all of the certificates it issued become invalid as well? What about for certificates issued by an authority beneath it? For example, if root ...
25
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2answers
9k views

Do SSL / X.509 certs cover all ports for a host?

Or are certs both host- and port-specific (excepting wildcard certs)? I would assume they aren't, because they're supposed to verify a domain, but at the same time I've never seen anyone run HTTPS on ...
24
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1answer
20k views

Which properties of a X.509 certificate should be critical and which not?

RFC5280's section 4.2 states Each extension in a certificate is designated as either critical or non-critical. A certificate-using system MUST reject the certificate if it encounters ...
23
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3answers
26k views

What is the use of cross signing certificates in X.509?

In X.509 architecture what are the uses of cross signing certificates from other hierarchy? Does it just expand trust? So from the answer I am assuming that if CA3 is cross signed by CA2 (from ...
22
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1answer
10k views

Relationship between RSA, Diffie-Hellman Key Exchange, PKI and X.509?

I am getting confused with RSA, Diffie-Hellman Key Exchange, PKI and X.509v3. I took a look of RSA's mathematics algorithm, it seems like a encryption algorithm, right? Generating public key and ...
20
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4answers
9k views

Can an intermediate CA be trusted like a self-signed root CA?

Is it possible within the limits of the X.509 specification to mark an intermediate CA as trusted for a specific purpose, e.g. to verify a VPN, HTTPS etc. server key, just like it would work with a ...
16
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4answers
6k views

Why is it a good idea that X.509 digital certificates have an expiry date?

What is the benefit of having certificates expire at some fixed date?
15
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5answers
19k views

A standard way to manually add a digital signature to a pdf file?

I've created a few certificates to use myself, but I find myself stumped when it comes to creating a certificate which contains a digital signature. First, how would I go about creating a standard ...
14
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2answers
4k views

How long can X.509 certificate chains be?

Usually, I only see certificate chains with a root CA, an intermediate one, and a third one for the particular SSL/TLS website; but can X.509 certificate chains be deeper than 3 levels? Is there a ...
14
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2answers
9k views

Are certificate authorities required to obey to the signature algorithm (hashing) specified in the CSR?

I was playing a little bit with signature algorithms, trying to determine which CAs among the ones I use are currently issuing SHA2 certificates. I generated a CSR specifying the SHA256 hash (either ...
14
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2answers
22k views

How is an X509 certificate signer verified?

Lets say I create a self-signed X509 certificate A and use it to issue certificate B. I put certificate A in my trusted root authorities so that all certificates signed by it are accepted. My question ...
13
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2answers
11k views

What is the difference of TrustManager PKIX and SunX509?

Java's JSSE provides two different TrustManagers: PKIX and SunX509 I tried to find out what the differences between both are, but couldn't find any in the documentation. Can you tell me the ...
13
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1answer
15k views

Encrypting local HTTP traffic using a self-signed certificate

For the past couple of hours I've been trying to create a self-signed certificate which I'd like to use to encrypt HTTP traffic between computers and a server on my home network (because I'm paranoid ...
12
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2answers
249 views

Who was in the first set of CAs

I am currently digging into the history of SSL/TLS. I found that netscape introduced SSL around 1994/1995. They obviously decided to go with a X.509 PKI to mitigate MitM attacks. I, however, could not ...
12
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1answer
2k views

Are X.509 nameConstraints on certificates supported on OS X?

I have the following "chain" of certificates on a test machine right now: A self-signed CA cert, in my Keychain and trusted & trusted by Firefox. A CA cert with with the following, X509v3 Name ...
12
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2answers
3k views

How to properly create and use cross-signed CAs and certificates

I'm trying to create an environment with cross-signed CAs, and verify a certificate issued against one of the CAs, all using openssl. The best I got so far is getting openssl into an endless loop ...
11
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5answers
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How to validate a client certificate

My understanding is that when using a client certificate for security one issues a private and public key cert (for example X509) of some sort and sends that of to the consumer of the service that one ...
11
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2answers
12k views

Validating an SSL certificate chain according to RFC 5280: Am I understanding this correctly?

we're in the process of replacing certificates with SHA1 hash due to Google's move to let them appear less secure in Chrome. The replacement certificates use a different intermediate CA than the ones ...
11
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3answers
7k views

Creating an X.509 certificate with an invalid signature

Creating an X.509 certificate with a valid signature with OpenSSL is pretty well documented all over the Internet. There are instructions on creating certificates that are signed by themselves and ...
11
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1answer
6k views

The difference between Subject Key Identifier and sha1Fingerprint in X509 Certificates

I have some SW that extracts certificates data and the SW utilizes OpenSSL. I am confused what is the difference between the subjectKeyIdentifier and the sha1Fingerprint. Both are hash values. My ...
11
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1answer
17k views

Root certificate key usage (non-self-signed end entity)

This discussion does not include self-signed end entity certificates for hosts like web servers and mail servers. OpenSSL's default configuration for a CA certificate has the following keyUsage: ...
10
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3answers
2k views

Allowing the public to generate a CSR from your private key

As a hosting provider, I'd like to make the process of generating a certificate for a customer's domain as convenient as possible. I was pondering creating a webpage where anyone could: generate a ...
10
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4answers
1k views

Can a revoked certificate be re-instated?

If a certificate is revoked, can it be re-instated, or is the only option to generate a new one?
10
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2answers
5k views

Why one should prefer EST protocol instead of SCEP?

For many years SCEP was a simple and widely used protocol for obtaining X.509 certificates. However, not too so long ago another protocol called EST (RFC 7030) was developed. What are the main ...
10
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2answers
470 views

Correct settings to generate private intermediate CA

I am using 'xca' in Linux to set up a private CA. xca only includes templates for the Root CA and End-User CA, no intermediates. What are the correct settings (fields and flags) for an intermediate (...
9
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2answers
3k views

Definitions for CRL Reasons

Is there any authoritative definition of the various reasons possible in a CRL file? Section 6.3.2(b) of RFC5280 lists a few: unspecified keyCompromise cACompromise affiliationChanged superseded ...
9
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2answers
16k views

Recommended key usage for a client certificate

My program has the following flow: a client sends a CSR to server, the server sends back a client certificate and after that the client communicates with the server to a path that requires a ...
9
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2answers
21k views

Use openssl to individually verify components of a certificate chain

This is related to another question, How to verify a signature of one entity by another using OpenSSL CLI? I used openssl s_client -showcerts -connect www.google.com:443 to collect three certificates ...
9
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2answers
8k views

How to use a Yubikey NEO (or any OpenPGP card or GnuPG in general) to sign X.509 CSRs?

Since the Yubikey NEO can be used as an OpenPGP card (see here) with three 2048 bit RSA keys, I thought about creating a CA from one of its public keys. Since the private key cannot be extracted (...
9
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2answers
2k views

X.509 certificate policies question

I asked another question about certificate policy mappings. This is a different issue. This is about Certificate Policies. To quote from the X.509 RFC: In an end entity certificate, these ...
9
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1answer
11k views

Which extensions to use for a S/MIME certificate?

Analogously to the SSL server certificate question, which extensions should I use for S/MIME, and should the CA be restricted somehow as well? (I'm using openssl, which at the moment creates CA and ...
9
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1answer
2k views

Why is the Signature Algorithm listed twice in an x509 Certificate?

Section 4.1 of RFC 5280 defines the contents of an x509 Certificate. Specifically, two fields are listed (signatureAlgorithm and signature) and defined to contain the same information: ...
8
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2answers
881 views

Why don't banks sign their email using S/MIME?

If email sent by my bank included S/MIME signatures that my mail client can verify, then I would have the assurance that the mail was not tampered with or sent by some malicious third-party. Most ...
8
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2answers
4k views

ASN.1: ENUMERATED vs INTEGER

From the X.509 specs: CRLReason ::= ENUMERATED { unspecified (0), keyCompromise (1), cACompromise (2), affiliationChanged (3), ...
8
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1answer
4k views

Why do X.509 certificates have “Key Usage” attribute?

I can find their values and all details in the RFC, but I cannot find why it was decided to have this attribute in certificates, instead of leaving them to be multipurposes. Is there a reasoning ...
8
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2answers
9k 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 ?
8
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2answers
2k views

Enforce Code/Script Signing

I have both a couple of X.509 Code Signing certificates and a GPG keypair that I can use to sign against code I run on my VPS. Every now and again I write code for iOS, OS X and Windows and always ...
7
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3answers
3k views

What are the accepted naming convention for the terms “public/private keys” and “certificates”?

Is there an accepted naming convention for referring to PKI artifacts? There seems to be a lot of confusion with the naming of artifacts. For example, it seems that some people refer to: public ...
7
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1answer
17k views

Enhanced Key Usage vs. Extended Key Usage

I've seen both the terms Enhanced Key Usage and Extended Key Usage, and both were abbreviated as EKU. Do both refer to the same extension or property?
7
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2answers
2k views

Custom data in SSL certificate

I am looking for a way to add extra, custom data in a SSL server certificate issued by a standard CA. Is this possible? I want to get a SSL server certificate issued by a standard CA, so that it'll ...
7
votes
1answer
1k views

SSL - Null Prefix Attacks Still Possible?

At DEFCON 17 (2009) Moxie Marlinspike gave a talk were he was able to use a malformed certificate signing request to get SSL certs signed for domains he doesn't own. The gist of it was that for the ...