What is it?
A Digital Signature —is a mathematical algorithm routinely used to validate the authenticity and integrity of any data. Put simply, it can be considered as a numerical value that is represented as a sequence of characters.
Currently, everything revolves around computers. It is now a necessity to have the capability to sign a digital document. Special software is needed to create a digital signature.
A digital signature scheme typically consists of three algorithms.
• A key generation algorithm that randomly selects a public and private key pair from an extremely large set of possible keys.
• A signing algorithm that, given a message and a private key, produces a signature.
• A signature verifying algorithm that, given the message, public key and signature, either accepts or rejects the message’s claim to authenticity.
How do digital signatures work?
In a Public Key Encryption (PKE) scheme, a public and private key pair is generated. The public key is used to encrypt data and may be distributed openly to others. The private key decrypts the encrypted data and must always be kept secret. Just like the physical keys, used for locking (encrypting) and unlocking (decrypting).
To digitally sign a document, on the other hand, a private key is instead used to encrypt a piece of data and produce a digital signature whereas a public key is used to decrypt the signature and verify its authenticity. First, a sender puts a digital document through a hash algorithm to generate a unique hash value. Sender’s private key is then used to encrypt the hash value. The encrypted hash corresponds to the digital signature.
The document together with the signature can be sent to a verifier. The verifier uses the sender’s public key to decrypt the signature and obtain the hash value. The document can then be put through the same hash algorithm and produce another hash value. If the two hash values are identical, the verifier can be certain that the document has not been modified and the sender is authenticated.
Digital signatures are significantly more secure than conventional handwritten signatures since they provide the following properties:
