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Digital certificates ​

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Introduction ​

  • Digital signatures are a way of validating the authenticity of digital documents and identifying the sender (signing with a digital signature indicates that the original message, document or file is safe and has not been tampered with).

  • As mentioned earlier on, there are four main purposes of digital signatures:

    • authentication
    • non-repudiation
    • data integrity
    • confidentiality

  • A digital signature is a digital code which is often derived from the digital certificate (described below), although other methods of generating digital signatures will be described throughout this section.

  • This also needs a lot of processing time to encrypt everything in the message.

  • The following method, which is used to identify the sender and ensure the message was not tampered with, does not encrypt the messages but uses a generated numerical value known as a digest.

  • With this method, to actually identify the sender, it is not necessary to encrypt the whole message.

  • The plaintext message is put through a hashing algorithm which produces the digest.

  • For example, if the first page of this chapter was going to be sent, we could put it through a hashing algorithm (such as MD4) and it would produce a digest, for example, it might produce the following digest:

  • 873add9ed804fc5ce0338d2e9f7e0962

  • However, this method still is not safe enough, since the public key could be forged by a third party, which means the recipient still cannot be certain that the message came from a legitimate source.

  • Therefore, an even more robust system is needed to give confidence that the sender is really who they claim to be.

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  • A digital certificate is an electronic ‘document’ used to prove the online identity of a website or an individual.

  • The certificate contains a public key and other information identifying the owner of the certificate.

  • A digital certificate is issued by the certificate authority (CA) – they independently validate the identity of the certificate owner.

  • This is a list of the items commonly found on a digital certificate:

    • version number
    • serial number of certificate
    • algorithm identification
    • name of certificate issuer
    • validity (start date and expiry date of certificate)
    • company details
    • public key
    • issuer’s identifier
    • company’s identifier
    • signature algorithm used
    • digital signature

How a user can apply for a digital certificate ​

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