How does Digital Signature Work

What are Digital Signatures

Digital Signature is a type of signature used to check the integrity and accuracy of electronic documents. The primary use of digital signatures is to provide integrity, authentication, and nonrepudiation to electronic messages.

Digital signatures are kind of public-key cryptography in which we use two keys; these are a public key and private key. Private keys are only known by their owner, and a public key is known by everyone who wants to communicate with the owner. To verify a digital signature, the receiver checks the sender's private key to decrypt the signature and find the hash. The receiver establishes a hash of the original documents or message using the same algorithm used by the sender. Then it compares this hash to decrypted hash obtained from the signature. After performing this, if the value of two hashes matched then the signature is considered valid, and then the message is examined accurate and unaltered.

An example of a digital signature is that when we use software to sign documents such as PDFs and other files, many software programs, such as Adobe Acrobat, can create a digital signature using public-key cryptography.

Characteristics of Digital Signature

1. Authentication:  Authentication in digital signature refers to verifying the sender's identity and ensuring that the signature has not been tampered with. And digital signature provides various authentication measures, such as Public-key cryptography, digital signature, multi-factor authentication, and biometrics.
2. Security: Security is a one of the most important aspects of digital signatures, it used to check the integrity and availability of electronic documents. And some of the security measures of digital signature are
3. Public-key cryptography
4. Hashing
5. Timestamping
6. Revocation
7. Certificate Authorities
8. Non-repudiation: Nonrepudiation is one of the essential digital signature features, ensuring that electronic transactions are legally binding and cannot be denied by the sender. It also ensures the sender cannot deny signing the electronic message or document. And when a digital signature is created, it uses the sender's private key to encrypt a unique "fingerprint" of the document called a hash.
9. Integrity: Integrity is also essential for digital signature and ensuring that the contents of the document or message have not been tampered with since it was signed.
10. Efficiency: Digital signature are efficient and very easy to use, which allows users to sign and verify documents and message quickly. 

Working of Digital signature

The below diagram shows a working of digital signature. This Digital Signature uses private and public keys, and no one shares the private key. It also ensures that no one besides the sender can replicate the sender's signature, and everyone shares it as public. It helps to send a secure message to the receiver. And if both keys match, then a secure transaction takes place, and a verification process is used to verify the message's authenticity.

A digital signature is the type of electronic signature that uses a public-key cryptography to ensure the integrity and authenticity of electronic messages. Working of digital signature requires complicated procedure, and these steps provides a secure and good way to sign and verify electronic transactions.

Digital signature requires various steps:

• Hashing: it is the first step in working of a digital signature, and this step involves running the document through a cryptographic hash function that generates a fixed-length hash value. The hash function takes the input data, applies an algorithm, and produces an accurate, unique, fixed-length output. The hash value it produces a unique and represents its content in a secure form, and it is impossible to regenerate the original document from the hash.   

• Encryption:  Encryption is one of the most critical steps of the digital signature process. This encryption is based on public-key cryptography, which involves using a pair of private and public keys to encrypt and decrypt data. The sender controls the private key, and others share the public key. When the sender encrypts the hash value with their private key and then public key helps to decrypt the digital signature and find the hash value. This encryption process used in signature ensures that the digital signature is unique to the sender.
• Digital Signature:  Digital signature’s classification is based on the private and public critical systems, and also it hooked with the original document. This can be done by attaching the signature within a document or also by attaching it in a message file.

• Transmission: In this step, the digital signature will transmit through all the signed documents or messages to the receiver. And the signature can be transmitted separately as part of the signed document.

• Verification: Verification is most important step in the digital signature, and it is a method to authenticate the sender’s identity, used for checking the validity of the digital signature, and also checking that the document or message has not been tampered with during transmission and this verification process takes place with special software tools, which also used to verify the sender's identity, certificates status and the integrity of the signed document or message.

• Non-repudiation: Once the digital signature is verified, it ensures the nonrepudiation of the document. It provides applicability to digital signatures and makes them a trusted and more secure method to design and exchange documents.