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Hi I am a little new to security, but in researching digital certificates it seems the only format people describe is X.509.

Are there other formats? If so what are they and where can I find information on them?

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Google is always your best friend. A quick search came up with this and this. Is this what you mean? –  rath Dec 31 '13 at 12:34
@rath I do not think so :/ Your links list formats for X.509 certificates (to store or transmit them). But I think the question is whether there are other "quasi-standards" for certificates and PKI besides PKIX, i.e., RFC5280. But I may be wrong :) –  DrLecter Dec 31 '13 at 13:47
You might be right. I'm not familiar with that format anyway so I posted the links just in case. Cheers –  rath Dec 31 '13 at 13:51
Ok ;) One alternative that comes up to my mind is SPKI. But I am not sure if this approach ever has made it to some practical application. –  DrLecter Dec 31 '13 at 13:52
Thanks! This is great info. –  user3137124 Jan 2 at 15:16

2 Answers 2

Quote from http://www.digi-sign.com/node/10922

All Types of Digital Certificates Are Also a X509 Certificate

A X509 certificate *refers to all types of digital certificates, regardless of how they are utilized, and implies the current standardization used to design and create digital certificates. This standardization recognizes that the information, data and other embedded objects within a digital certificate are all placed exactly in the same location and in the same order. As a result, these standards make it possible for digital certificates of all kinds to be shared between individuals and organizations, as well as allow for applications to use a single digital certificate, in place of multiple certificates. For instance, word processing, spreadsheets, data bases, and presentation software suites can be designed to use a single digital certificate in order to authenticate the user and verify they have a valid copy of the software installed on their computer. Without the X509 standards, users would have to have one digital certificate for each application, regardless of whether it was bundled as a suite or purchased separately.

That's the reason why you keep seeing X509 everywhere.

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The title of that quote is a bit misleading ... it suggests that X.509 is a standard incorporating all other standards (or a format incorporating all other certificate formats), but actually it only says that every certificates for every use case can be expressed in X.509. –  Paŭlo Ebermann Jan 7 at 22:48

Although x.509 is the standard for PKIs with CAs, different certificate formats have been defined for the other 2 major PKI approaches:

  • SPKI has defined its own certificate format , still (forever?) in draft status.
  • Web-of-Trust models usually use the OpenPGP certificate format defined in RFC2440

RFC4212 "Alternative Certificate Formats for the Public-Key Infrastructure Using X.509 (PKIX) Certificate Management Protocols" may also be of interest.

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Thanks! Helps a lot! –  user3137124 Jan 2 at 15:17

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