Valicert Japan

an a signature be revoked?

A digital signature, as appended to some arbitrary message, cannot be revoked in and of itself. However, if the certificate used to sign the message is revoked at some point before the message is received, then when the signature is verified the user will be informed that the certificate is no longer valid. This underlines the importance of revoking your certificate immediately if it should ever be compromised by theft or other loss of the physical security necessary to protect it.

How can I check a signature?

Certificate-enabled applications are able to verify signatures automatically; no special effort is required by the user.

Do you provide notary services? Time stamping services?

No, and not specifically, though ValiCert does time-stamp its own transactions internally.

Is revocation relevant for more than certificates?

No, at least not yet. The notion of revocation in the electronic domain is unique to certificates since it is an action which can only be performed on them.

How is revocation different from validation?

Revocation is the process of marking a previously-valid certificate as invalid at and subsequent to the time of the revocation. Validation is the act of checking the status of a certificate to see whether or not it is currently revoked.

How is key recovery different from ?

Key recovery is the act of retrieving a copy of a private key when the original is lost or destroyed. is the act of marking a previously-valid certificate as hereafter invalid. Revocation is only useful if there is a validation mechanism in place which allows every transaction to be validated quickly and with no additional effort on the part of the end user.

What are some usage scenarios for the ValiCert server & service?

This is a huge question. Consult our main web site for more information and example scenarios.

What is the difference between a digital signature and a certificate?

A digital signature is a hashed representation of the source message, appended to the end of the message itself before the (optional) encryption process takes place. It is typically of a fixed length, regardless of the size of the signed message. A certificate is a container for carrying an individual’s public key, used for encrypting messages for that individual, and to verify signatures created by that individual.

Do you support PGP certificates?

No.

How does my CA sign up for the service?

Ask your CA to contact us directly; it is highly likely that they already have a relationship with ValiCert.

If a certificate comes back revoked, what do I do?

That depends on the nature of the transaction for which the certificate was used. If your mother sent you email with a certificate that expired two days ago, you can simply suggest that she get it renewed. If, on the other hand, a former trader in your brokerage tries to perform a $10 million transaction ten minutes after being fired, then you can be glad you revoked that certificate promptly.

When do I know a certificate is revoked?

Your application will alert you to the presence of a revoked certificate.

Who revoked my certificate?

Either your CA, or a designated official trusted by your CA, revoked your certificate.

How can I revoke yours?

Unless you are a CA or a designated official trusted by a CA, you can’t revoke other certificates.

Who are Alice & Bob?

Alice and Bob are the First Couple of Cryptography. They are often used as example users when explaining cryptosystems.