Glossary
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ARL
     The Authority Revocation List is technical identical to a CRL but used for CAs and not for end user certificates.

Chain model
     Verification model for X.509 which uses the creation date of a signature as the date the validation starts and in turn checks that each certificate has been issued within the time frame, the issuing certificate was valid.  This allows the verification of signatures after the CA's certificate expired.  The validation test also required an online check of the certificate status.  The chain model is required by the German signature law.  See also Shell model.

CMS
     The Cryptographic Message Standard describes a message format for encryption and digital signing.  It is closely related to the X.509 certificate format.  CMS was formerly known under the name PKCS#7 and is described by RFC3369.

CRL
     The Certificate Revocation List is a list containing certificates revoked by the issuer.

CSR
     The Certificate Signing Request is a message send to a CA to ask them to issue a new certificate.  The data format of such a signing request is called PCKS#10.

OpenPGP
     A data format used to build a PKI and to exchange encrypted or signed messages.  In contrast to X.509, OpenPGP also includes the message format but does not explicitly demand a specific PKI.  However any kind of PKI may be build upon the OpenPGP protocol.

Keygrip
     This term is used by GnuPG to describe a 20 byte hash value used to identify a certain key without referencing to a concrete protocol. It is used internally to access a private key.  Usually it is shown and entered as a 40 character hexadecimal formatted string.

OCSP
     The Online Certificate Status Protocol is used as an alternative to a CRL.  It is described in RFC 2560.

PSE
     The Personal Security Environment describes a database to store private keys.  This is either a smartcard or a collection of files on a disk; the latter is often called a Soft-PSE.

Shell model
     The standard model for validation of certificates under X.509.  At the time of the verification all certificates must be valid and not expired. See also Chain model.

X.509
     Description of a PKI used with CMS.  It is for example defined by RFC3280.