Digital Signatures

Question 1

Digital Signature

Answer 1

Digital signature is a process that guarantees that the contents of a message have not been altered in transit.

Only the senders public key can decrypt the encrypted hash - if the message arrives with a different hash the recipient knows the message has been altered.

Question 2

Digital Signature Example

Answer 2

Alice sends an email to be digitally signed - the hash value is calculated by Alice’s computer.

The hash value is encrypted using her signing key to create the DS.

The email is sent to Bob.

Bob’s email app identifies the message has been signed and proceeds to decrypt it using Alice’s private key, calculate the hash and then compare the hash of email content. Any hash differences = tampered message.

Question 3

Certified Signatures

Answer 3

Adding a certifying signature to a document indicates you are the author and want to secure the document against tampering.

Contains the name of the document signer and the certificate issuer to indicate the authorship and authenticity of the document.

Question 4

Approval Signatures

Answer 4

Approval signatures can be set in a business workflow to help optimise approval procedures.

They involve capturing approvals made by individuals and embedding them within the PDF. Allows them to include details such as an image of a signature, date, location and seal.

Question 5

Visible Digital Signatures

Answer 5

These allow a single user or multiple users to digitally sign a single document.

The signatures would appear on the document in the same way as the signatures are applied to a real document.