wiki:FrameworkCertificates

X.509v3 Certificates used in SPARTA

In SPARTA Framework X.509v3 certificates are used to hold user information.

In our user centric approach the public/private key pair associated to a certificate are always generated by the user. Public Key is stored into the certificate. The legitimate owner of the certificate is thus the user who owns the corresponding private key, which NEVER leaves the user terminal. It is important to underline that the public/private keys are NOT employed to link the real identity of the user who generated. Instead, they are used by the latter to anonymously prove she is the legitimate owner of a given certificate.

Certificates defined in the Sparta Framework are:

  • User certificate:
    • Issuer: Service Provider
    • Contains: Encrypted user identity, represented by a certificate-bound public key (the owner of the corresponding Private Key is not disclosed!!)
    • Description: Encryption over real User identity is made with a secret known only by the SP. Hence only SP knows the real identity of the user who owns the corresponding Private Key.
  • Pseudonym certificate:
    • Issuer: Identity Repository (IR) or the Service Provider itself
    • Contains: pseudonym (represented by a certificate-bound public key) + optional service related extensions
    • Description: It's the last "token" obtained after multiple iteration of the handshake protocol with different IRs. A first token is issued by an IR after user submits her User Certificate. A second token can be obtained by submitting the first token to another IR. Iterating the previous step, user creates a chain of IRs, whose last ring can be the SP itself.

Note that: access credentials are NOT contained into the Pseudonym Certificate, but into a standalone file generated as a Marked Blind Signature over the cashcard (see below).

  • Grant Certificate:
    • Issuer: The Bank
    • Contains: Grant Value, AS_ID, certificate-bound public key (again, identity of the user who owns the corresponding private key is not disclosed).
    • Description: The Grant value is the maximum amount in € covered by the Bank for the owner of the certificate (i.e. the User holding the private key). The AS_ID identifies the only AS that can receive this certificate
  • Cash Card:
    • Issuer: Accounting Server (AS)
    • Contains: Grant Value + other optional service related extensions, certificate-bound public key (again, identity of the user who owns the corresponding private key is not disclosed).
    • Description: it works like a credit card but the real identity of the owner is not disclosed. The user is able to make anonymous payments for amounts that are less than grant.

Note that: to access the service the user will need also access credentials which are contained into a standalone file, issued by the SP after the User requests a Marked Blind Signature over the cashcard.

Last modified 11 years ago Last modified on Dec 10, 2007, 11:52:09 AM