Digital Signature: How Does It Work?

A digital signature is simply a mathematical technique that is adopted to verify the authenticity and legitimacy of a message, software, or digital document. To simply put, it is the digital equivalent of a handwritten signature or stamped seal, but, unsurprisingly, it provides far more inherent security. The aim of a digital signature is to offer a solution to the problem of tampering and impersonation in digital communications.

Another thing a digital signature does is that it can offer proof of identity, origin, and status of electronic documents. It can also be used by signers to acknowledge informed consent. In several countries, it is considered to be legally binding in a similar way as traditional handwritten document signatures.

How does a digital signature work?

A typical digital signature is based on public-key cryptography – which is also known as asymmetric cryptography. By using a public key algorithm, including RSA (which stands for Rivest-Shamir-Adleman), two keys are created, thereby generating a mathematically linked pair of keys, one of which is private and the other public.

A digital signature does its work via public key cryptography's two mutually verifying cryptographic keys. Anyone who generates the digital signature uses a private key to encrypt signature-related data, and the only feasible way to decrypt that data is with the signer's public key. If the recipient is unable to open the document by using the signer's public key, it shows that there is an issue with the signature or the document. This is basically how digital signatures are verified.

Just like the Bitcoin System app, one of the requirements of digital signature technology is that anyone who generates the signature must keep the private key secret. If anyone else gets access to the private signing key, they could generate a fraudulent digital signature in the private key holder's name.

What are the benefits derived from digital signatures?

One of the top benefits of using a digital signature is to assure security. The security capabilities that are associated with the digital signatures ensure that a document is not tampered with and the signatures are authentic. Certain security features and methods are used in digital signatures. Some of these include:

• Personal Identification Numbers, codes, and passwords. These are used in verifying a signer's identity. Emails, passwords, and usernames are also used.
• Asymmetric cryptography: This adopts a public key algorithm, including private and public-key encryption and authentication.
• Checksum: This involves a long string of letters and numbers that represents the sum of the correct digits in a piece of digital data, against which comparisons can be made to spot errors or changes. A checksum can perform the role of a data fingerprint.
• Cyclic redundancy check (CRC): This is an error-spotting code and verification characteristic that can be used in digital networks and storage devices to detect changes made to raw data.
• Certificate authority (CA) validation: Certificate Authorities can issue digital signatures and act as trusted third parties by accepting, verifying, issuing, and maintaining digital certificates. Using a Certificate Authority helps in avoiding the generation of fake digital certificates.

How to generate a digital signature

In order to generate a digital signature, it is important to use signing software, including an email program to provide a one-way hash (a fixed-length string of letters and numbers generated by an algorithm) of the electronic data to be signed.

The digital signature owner's private key can be used to encrypt the hash. This encrypted hash – alongside other data, including the hashing algorithm – is the digital signature. The encryption of the hash instead of the entire message is done because a hash function is capable of converting a random. input into a fixed-length value. This saves time since hashing is faster than signing. The hash value is unique to the hashed data. Any change in the data, even if it is a change in a single character, will lead to a different value. This attribute ensures that others can use the signer's public key to decrypt the hash to verify the legitimacy of the data.

Is there a need to use PKI or PGP with a digital signature?

Digital signatures often adopt the PKI standard and the Pretty Good Privacy (PGP) encryption program. This is because both minimize any potential issues related to security that is associated with transmitting public keys. They confirm that the sender's public key belongs to that individual and validate the sender's identity.

PKI is a platform for services that create, distribute, control and make accounts for public-key certificates. PGP is simply a variation of the PKI standard that uses both the symmetric key and public-key cryptography, but it finds a difference in how it associates public keys to user identities. PKI uses a Certificate Authority to verify the authenticity and attach a user identity with a digital certificate. On the other hand, PGP uses a web of trust. Users of PGP decide on who they trust and which identities get verified.

Bottom Line

How effective a digital signature depends considerably on the strength of the private key security. Using a digital signature, as explained above, is relatively easy. However, without PKI or PGP, it becomes impossible to ascertain someone's identity or revoke any compromised key, and it becomes easier for people with illicit agendas to impersonate people.