The correct answer is C. cryptography.
Cryptography is the science of secret writing. It is used to protect information from unauthorized access or disclosure. Digital signatures are a type of cryptography that is used to verify the authenticity of digital documents. They are created using a mathematical algorithm that is based on a secret key. The secret key is used to encrypt the document, and the digital signature is the encrypted version of the document. When someone receives a digital document, they can verify its authenticity by decrypting the document using the public key that is associated with the sender’s secret key. If the document decrypts correctly, then it is authentic.
HTML is a markup language that is used to create web pages. It is not used to create or verify digital signatures.
A programme is a set of instructions that is used to perform a task. It is not used to create or verify digital signatures.
Graphical coding is a type of coding that is used to create images. It is not used to create or verify digital signatures.