Digital signature

A digital signature is a process wherein a digital code is attached to an electronically transmitted document to validate the integrity of the document and the identity of the sender.

Creating a digital signature

A digital signature can be created by performing two steps:

1. Create a hash (message digest) of the message.
2. Encrypt the hash with the private key of the sender.

The following table shows how to create a digital signature:

Figure 9.9 – Digital signature

Now, let's discuss hash values and message digests.

What is a hash or message digest?

A hash function is a mathematical algorithm that provides a unique fixed string for any given message. Note that the hash value will be unique for each message. Let's understand this by looking at the following table:

Figure 9.10 – Hash values

The following software shows the hash value of the message Meeting at 8 AM...