Written signatures have been used to verify documents since at least the 17th century. They are used on countless types of agreements, from job contracts and credit card receipts to international treaties. But the digital age has ushered in new ways to communicate, no longer bound by paper and physical mailboxes. So how can we verify digital messages? The solution is digital signatures.
Here we will demystify the concept of digital signature systems to help you understand why they are chosen, and to develop a better understanding of their place in blockchain technology. Let’s start with what is digital signature and how it works:
What is Digital Signature and How it Works
A digital signature is a cryptographic mechanism used to verify the authenticity and integrity of digital data. In simple terms, it is a code that is attached to a message or document. After being generated, the code acts as proof that the message hasn’t been tampered with along its way from sender to receiver. We may thus consider it as a digital version of the ordinary handwritten signatures, but with higher levels of complexity and security.
Just as written signatures tie a person to a particular document, digital signatures cryptographically link an identity to a message. They are almost impossible to forge because they are based on number theory. In what is called “public key cryptography”, users own a public key and a private key, which form a pair. Public key cryptography uses encryption to guarantee security and protect sensitive key information. The public key represents the owner’s identity and the private key is secret, allowing them to prove they own the public key.
Let’s say Alice wants to send an encrypted message to Bob. Anyone can see Bob’s public key, so Alice can use it in the algorithm that encrypts her message. Observers can see or intercept the encrypted message but they can't decrypt it without Bob’s private key, which only he knows. So Alice can ensure nobody but Bob can see the message unless they have his private key.
For digital signatures, the operation is reversed. Instead of doing the initial computation with a public key, Alice uses her private key in the signing algorithm to link a signature to her message and public key. No one can derive Alice’s private key, or forge a valid signature for her, using only her signature and public key. However, anyone who knows Alice’s public key can easily verify that the message was signed by her private key.
Importance Of Digital Signatures
Digital signatures are often used to achieve three results: data integrity, authentication, and non-repudiation.
- Data integrity: Bob can verify that Alice’s message wasn’t changed along its way. Any modification in the message would produce a completely different signature.
- Authenticity: As long as Alice’s private key is kept in secret, Bob can use her public key to confirm that the digital signatures were created by Alice and no one else.
- Non-repudiation: Once the signature has been generated, Alice won’t be able to deny having signed it in the future, unless her private key gets somehow compromised.
Use Cases Of Digital Signatures
Digital signatures can be applied to various kinds of digital documents and certificates. As such, they have several applications. Some of the most common use cases include:
- Information Technology: To enhance the security of Internet communication systems.
- Finance: Digital signatures can be implemented to audits, expense reports, loan agreements, and much more.
- Legal: Digital signing of all sorts of business contracts and legal agreements, including governmental papers.
- Healthcare: Digital signatures can prevent fraud of prescriptions and medical records.
- Blockchain: Digital signature schemes ensure that only the rightful owners of the cryptocurrencies are able to sign a transaction to move the funds (as long as their private keys aren’t compromised).
Limitations Of Digital Signatures
The major challenges faced by digital signature schemes rely on at least three requirements:
- Algorithm: The quality of the algorithms used in a digital signature scheme is important. This includes the choice of reliable hash functions and cryptographic systems.
- Implementation: If the algorithms are good, but the implementation is not, the digital signature system will likely present flaws.
- Private Key: If the private keys get leaked or somehow compromised, the properties of authenticity and non-repudiation will be invalidated. For cryptocurrency users, losing a private key may result in significant financial losses.
Closing Thoughts
Digital signatures carry a lot of weight in the blockchain realm, where they are used to sign and authorize cryptocurrency transactions. They are particularly important for Bitcoin because the signatures ensure that coins can only be spent by the individuals that possess the corresponding private keys.
A great portion of today’s bureaucracy is still based on paperwork and although we’ve been using both electronic and digital signatures for years, there is still a lot of room for growth. Hence, learning what is digital signature and how it works now, will surely benefit you sometime down the line as we will likely see the increased adoption of digital signature schemes as we migrate to a more digitized system.
