Certificate Encoding#Certificates maybe encoded in using different Encoding formats.
Because all MIME-compliant clients can decode Base64 files, this format might be used by certification authorities that are not on computers running Windows Server 2003, so it is supported for interoperability. Base64 certificate files might use the .cer extension.
Privacy-Enhanced Mail (PEM) (Usually same as the base64)#Privacy-Enhanced Mail certificates usually have extentions such as .pem, .crt, .cer, and .key. Distinguished Encoding Rules (Distinguished Encoding Rules) Certificate and imply it is in Canonical Encoding Rules. Usually, certificates would not be exported in Canonical Encoding Rules format and the certificate is most likley Privacy-Enhanced Mail.
CRT #Probably this is Privacy-Enhanced Mail
Public Key Cryptography Standards (PKCS)#Produced by RSA Labs. Specifies format of objects used during public key operations In cryptography, PKCS refers to a group of Public Key Cryptography Standards devised and published by RSA Security.
- Language is ASN.1
- Implemented in RSAREF and BSAFE libraries
- Standards from IETF PKIX working group are a superset and generally compatible
- Three parts; all are optional
- Signature (with signer information)
- Include all three: opaque signing
- Omit content: detached signature
- Only certificates: “certs only”
- Used for set/list/chain of certificates
- File extension = .p7c (or .p7b)
- IETF Standard for "secure electronic mail"
- Digital signatures
- Need canonical form of message to be signed
- Other information for recipient
- Certificates for verification
- Sender's public encryption key (certificate)
- Sender's cryptographic algorithms
Example S/MIME (Signed)#
From: Eric Norman <email@example.com> MIME-version: 1.0 Content-type: multipart/signed; protocol="application/pkcs7-signature"; boundary=Apple-Mail-3-2162327; micalg=sha1 --Apple-Mail-3-2162327 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; format=flowed Message text --Apple-Mail-3-2162327 Content-Transfer-Encoding: base64 Content-Type: application/pkcs7-signature; name=smime.p7s Content-Disposition: attachment; filename=smime.p7s MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIGQzCCAsMw ggIsoAMCAQICAgMzMA0GCSqGSIb3DQEBBAUAMIG3MQswCQYDVQQGEwJVUzESMBAGA1UECBMJV2lz ... snip ... icLcyxUobN5sT+ttMbm1S6Q+6wAAAAAAAA== --Apple-Mail-3-2162327--Netscape Certificate Sequence is another PKCS#7 object format, and like the SignedData format, it allows multiple certificates to be imported together. This format is simpler than the PKCS#7 SignedData object format. It consists of a PKCS#7 ContentInfo structure, wrapping a sequence of certificates.