Cryptography Reference
In-Depth Information
CA2
CA3
CA1
Bob
Alice
Figure 11.7.
A simple CA topology
topology Alice has a relationshipwithCA1, which is a low-level CAwhose root CA
is CA2. Bob has a relationship with CA3, which has cross-certified with CA2. Now
suppose that Bob wishes to verify Alice's public-key certificate. To do so, he will
need to verify a certificate chain that consists of the three public-key certificates
shown in Table 11.2.
In other words, Bob first verifies Alice's public-key certificate, which is signed
by CA1. Then Bob needs to verify CA1's public-key certificate, which is signed by
CA2. Finally, Bob verifies CA2's public-key certificate, which is signed by CA3.
The certificate chain ends at CA3, since this is the CA that Bob has a relationship
with and thus we assume that he trusts signatures by CA3.
Indeed, to properly verify the above certificate chain, for
each
of these public-
key certificates Bob should:
1. verify the signature on the public-key certificate;
2. check all the fields in the public-key certificate;
3. check whether the public-key certificate has been revoked.
Table 11.2:
Example of a certificate chain
Certificate
Containing public key of
Certified by
1
Alice
CA1
2
CA1
CA2
3
CA2
CA3
