Card Verifiable Certificate

A Card Verifiable Certificate ( CVC ) is a public-key certificate that is stored in a very compact format. Objective of the development was a verification of the certificate by smart cards, which are subject to strong resource limitations in memory and processing power to enable.

Motivation

If a smart card will verify the authenticity of an accessing apply to them, mainly symmetric challenge-response methods are currently used. For this, a symmetric key is stored on the card during the card manufacturing or personalization. The disadvantage here is that for any party that needs to authenticate later over the map, already a corresponding key must be present during the production. A subsequent extension is later no longer possible.

The process can be simplified considerably if a PKI is established. Then only the public key of a root CA is stored in the card during the card production. All parties who wish to access later on the card, can receive and authenticate so that any time a private certificate from the CA ( or a subordinate CA).

Certificate Format

Certificates in X.509 format require a relatively large storage space and make due to their flexibility, the use of a complex algorithm for the evaluation required. CVCs avoid these problems. Since they are only used for authentication, only the following information is relevant:

  • Issuing CA
  • Certificate holder
  • Possibly with the certificate associated access rights
  • Public key of the certificate holder
  • Validity period

Self-describing CVCs

By encoding using the Distinguished Encoding Rules of ASN.1 standards, these certificates can be interpreted without further aids. Here, each data field is provided a day and a length specified above. The tag in this case indicates the type of the subsequent data field. The standard ISO 7816-6 lists the allowed types.

Not self-describing CVCs

Unlike self- descriptive certificates are missing in this type of certificate and day length specification. In order to interpret the data is a header required list containing the missing data. Together with the certificate data, the individual fields can be isolated.

By omitting the header elements, the certificate does not waste space. However, the smart card must be given a list header before the verification of certificates of this type. This can happen when the card producing or before beginning a certificate verification by the command MANAGE SECURITY ENVIRONMENT.

Signature creation

To save even more space, the signature is not appended to the certificate data but is part of the certificate. For this purpose, the value defined in ISO 9796 signature algorithm with message recovery is employed. At first, the hash value of the entire certificate data is formed and afterwards divided. The first part is encrypted together with the hash value with the private signature key. This recoverable part of the data, together with the second portion of the data, the non- recoverable part of the certificate.

Verification

To verify the recoverable part of the data with the public signature verification key is decrypted, separated the hash value and the remaining data associated with the non- recoverable part of the data. From these data, a hash value is again formed, and this is compared with the signed hash. If a match between the two values ​​is to ensure that the certificate data has not been tampered with.

Use

  • As part of the electronic health card ( health card ) is planned to equip the card with a reload functionality. So to be created subsequently other uses for the card. For this purpose, the card management system of the respective health insurance must authenticated against the map. This CVCs may be used.
  • On issue of a eRezepts that is stored on the electronic health card, the electronic health professional card of the issuing doctor against the card has to authenticate with his CVC as part of a Card to Card Authentication.
  • The electronic passport protects sensitive data, such as fingerprints using EAC. To access the data, the reader must identify with his CVC against the ePassport identity card or his permission to read the relevant data.
  • The new German ID card, a reader before reading any data from the chip must demonstrate possession of the necessary authorization by EAC and a CVC ( Certificate of Eligibility ).

Standards

The format of CV Certificates in ISO 7816 - Part 8 specifies.

  • Digital certificates
  • Smart card
Challenge–response authentication Chantiers Aéro-Maritimes de la Seine
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