Method and apparatus for external organization path length validation within a public key infrastructure (PKI)

1. An external organization path length (EOPL) validation method, the method comprising:

at a relying party node of an organization:

receiving an authentication request from a subject node of an external organization;

obtaining and evaluating certificates from a chain of certificates that link the subject node to a trust anchor of the relying party node wherein, at least one certificate from the chain of certificates comprises at least one of:

an enabled External Organization Flag (EOF) that indicates whether the certificate was issued to a node affiliated with the external organization, and

an External Organization Path Length Constraint (EOPLC) value that specifies a value equal to a maximum allowable number of certificates within the chain of certificates that are permitted to include an EOF that is enabled;

determining whether a total number of enabled EOFs from certificates in the chain of certificates exceeds a lowest EOPLC value from certificates in the chain of certificates; and

invalidating authentication of the subject node when the total number of enabled EOFs from certificates in the chain of certificates exceeds the lowest EOPLC value from certificates in the chain of certificates.

2. The EOPL validation method of claim 1 , wherein each of the organization and the external organization comprises at least one node and at least one trust anchor.

3. The EOPL validation method of claim 1 , wherein a public key infrastructure (PKI) of the organization is different from a PKI of the external organization.

4. The EOPL validation method of claim 1 , wherein obtaining and evaluating certificates from the chain of certificates comprises:

iteratively obtaining one or more certificates from the chain of certificates;

determining whether the one or more certificates comprise the enabled EOF; and

determining whether the one or more certificate comprise the EOPLC value.

5. The EOPL validation method of claim 4 , further comprising:

maintaining, in memory at the relying party node, an EOPL counter; and

incrementing the EOPL counter by one each time the one or more certificates comprise the enabled EOF; and

determining the total number of enabled EOFs from certificates in the chain of certificates based on a value of the EOPL counter.

6. The EOPL validation method of claim 4 , further comprising:

storing, in memory at the relying party node, a current external organization path length constraint (current EOPLC) value;

prior to evaluating certificates in the chain of certificates, initializing the current EOPLC value stored in memory to infinity; and

replacing the current EOPLC value stored in memory with the EOPLC value from the one or more certificates each time when the EOPLC value from the one or more certificates is lower than the current EOPLC value stored in memory; and

determining the lowest EOPLC value from certificates in the chain of certificates based on the current EOPLC value stored in memory.

7. The EOPL validation method of claim 1 , further comprising:

upon invalidating authentication of the subject node, transmitting a message from the relying party node to the subject node conveying that authentication has failed.

8. The EOPL validation method of claim 1 , wherein each certificate in the chain of certificates is a public key certificate issued by a certification authority and further comprises:

an issuer field identifying a name of the certification authority that issued the digital public key certificate;

a subject field identifying a node trusted by the certification authority specified in the issuer field;

a public key of the node specified in the subject field;

a basic constraints field comprising a path length constraint; and

a digital signature of the certification authority comprising: a private key of the certification authority that issued the digital public key certificate.

9. The EOPL validation method of claim 7 , wherein the public key certificates comprise X.509 compliant public key certificates.

10. The EOPL validation method of claim 1 , wherein the chain of certificates comprises at least:

one certificate that is issued to the subject node and that identifies the subject node as a subject, and

another certificate that is issued and signed by the trust anchor of the relying party node.

11. The EOPL validation method of claim 1 , wherein the trust anchor comprises a root certification authority for the organization.