What is the difference between a cer, pvk, and pfx

Question

What is the difference between a cer, pvk, and pfx file? Also, which files do I keep and which am I expected to give to my counter-parties?

Answer 1

Windows uses .cer extension for an X.509 certificate. These can be in "binary" (ASN.1 DER), or it can be encoded with Base-64 and have a header and footer applied (PEM); Windows will recognize either. To verify the integrity of a certificate, you have to check its signature using the issuer's public key... which is, in turn, another certificate.

Windows uses .pfx for a PKCS #12 file. This file can contain a variety of cryptographic information, including certificates, certificate chains, root authority certificates, and private keys. Its contents can be cryptographically protected (with passwords) to keep private keys private and preserve the integrity of root certificates.

Windows uses .pvk for a private key file. I'm not sure what standard (if any) Windows follows for these. Hopefully they are PKCS #8 encoded keys. Emmanuel Bourg reports that these are a proprietary format. Some documentation is available.

You should never disclose your private key. These are contained in .pfx and .pvk files.

Generally, you only exchange your certificate (.cer) and the certificates of any intermediate issuers (i.e., the certificates of all of your CAs, except the root CA) with other parties.

Answer 2

In Windows platform, these file types are used for certificate information. Normally used for SSL certificate and Public Key Infrastructure (X.509).

• CER files: CER file is used to store X.509 certificate. Normally used for SSL certification to verify and identify web servers security. The file contains information about certificate owner and public key. A CER file can be in binary (ASN.1 DER) or encoded with Base-64 with header and footer included (PEM), Windows will recognize either of these layout.
• PVK files: Stands for Private Key. Windows uses PVK files to store private keys for code signing in various Microsoft products. PVK is proprietary format.
• PFX files Personal Exchange Format, is a PKCS12 file. This contains a variety of cryptographic information, such as certificates, root authority certificates, certificate chains and private keys. It’s cryptographically protected with passwords to keep private keys private and preserve the integrity of the root certificates. The PFX file is also used in various Microsoft products, such as IIS.

for more information visit:Certificate Files: .Cer x .Pvk x .Pfx

Answer 3

I actually came across something like this not too long ago... check it out over on msdn (see the first answer)

in summary:

.cer - certificate stored in the X.509 standard format. This certificate contains information about the certificate's owner... along with public and private keys.

.pvk - files are used to store private keys for code signing. You can also create a certificate based on .pvk private key file.

.pfx - stands for personal exchange format. It is used to exchange public and private objects in a single file. A pfx file can be created from .cer file. Can also be used to create a Software Publisher Certificate.

I summarized the info from the page based on the suggestion from the comments.

Answer 4

Here are my personal, super-condensed notes, as far as this subject pertains to me currently, for anyone who's interested:

• Both PKCS12 and PEM can store entire cert chains: public keys, private keys, and root (CA) certs.
• .pfx == .p12 == "PKCS12"
  • fully encrypted
• .pem == .cer == .cert == "PEM"
  • base-64 (string) encoded X509 cert (binary) with a header and footer
    • base-64 is basically just a string of "A-Za-z0-9+/" used to represent 0-63, 6 bits of binary at a time, in sequence, sometimes with 1 or 2 "=" characters at the very end when there are leftovers ("=" being "filler/junk/ignore/throw away" characters)
    • the header and footer is something like "-----BEGIN CERTIFICATE-----" and "-----END CERTIFICATE-----" or "-----BEGIN ENCRYPTED PRIVATE KEY-----" and "-----END ENCRYPTED PRIVATE KEY-----"
  • Windows recognizes .cer and .cert as cert files
• .jks == "Java Key Store"
  • just a Java-specific file format which the API uses
    • .p12 and .pfx files can also be used with the JKS API
• "Trust Stores" contain public, trusted, root (CA) certs, whereas "Identity/Key Stores" contain private, identity certs; file-wise, however, they are the same.