Digital Signature

Digital signature is mathematical equivalent of a handwritten signature on a physical document (such as a cheque book).

It serves the purpose of validating documents and ensure non-repudiation.

What is non-repudiation?

non-repudiation is a scheme that ensures that the signatory of a document can't deny the terms of the signed document.

Here is a visual representation of how digital signatures work.

If you are familiar with R, you can simulate the above scenario using the below code [others, please skip the coding section]

> library(sodium)
# Generate signature keypair for Alice
> privkey <- sig_keygen()
> pubkey <- sig_pubkey(privkey) 

> msg <- serialize("i shall give Bob  10 coins", NULL)

# Sign the message with private key (Alice signs the message)
> sig <- sig_sign(msg, privkey)
> print(sig)

# The bank can verify the message using the known public key of Alice
sig_verify(msg, sig, pubkey)