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Heartbleed is a security bug in some outdated versions of the OpenSSL cryptography library, which is a widely used implementation of the Transport Layer Security (TLS) protocol.
There are two different states of revocation defined in RFC 5280: Revoked A certificate is irreversibly revoked if, for example, it is discovered that the certificate authority (CA) had improperly issued a certificate, or if a private-key is thought to have been compromised.
If revocation status is unavailable (which may be benign or due to an attack), a client is faced with a dilemma when evaluating a certificate: it may fail-soft and assume that the certificate is still valid; or it may fail-hard and assume that the certificate has been revoked.
The OCSP responder uses the certificate serial number to look up the revocation status of Alice's certificate. The OCSP responder looks in a CA database that Carol maintains. In this scenario, Carol's CA database is the only trusted location where a compromise to Alice's certificate would be recorded.
The only increased risk of OCSP stapling is that the notification of revocation for a certificate may be delayed until the last-signed OCSP response expires. As a result, clients continue to have verifiable assurance from the certificate authority that the certificate is presently valid (or was quite recently), but no longer need to ...
X.509 also defines certificate revocation lists, which are a means to distribute information about certificates that have been deemed invalid by a signing authority, as well as a certification path validation algorithm, which allows for certificates to be signed by intermediate CA certificates, which are, in turn, signed by other certificates ...
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Without revocation, an attacker would be able to exploit such a compromised or mis-issued certificate until expiry. [15] Hence, revocation is an important part of a public key infrastructure. [16] Revocation is performed by the issuing certificate authority, which produces a cryptographically authenticated statement of revocation. [17]