Digital signature facts for kids
A digital signature is like a super-secure electronic stamp that proves who sent a digital message or document and that it hasn't been changed. It uses a special kind of secret code, called asymmetric cryptography, to make sure you can trust what you receive online. Think of it as a digital version of your handwritten signature, but much harder to copy!
Digital signatures are created using cryptography, which is the science of secure communication. They help make sure that the person who signed a message can't later say they didn't sign it, as long as their secret key stays safe. This is called acknowledgement. Many countries, like the United States, countries in Europe, and India, use digital signatures for important documents in government and businesses. For example, in India, a Digital Signing Certificate (DSC) is often used for filing business papers and tax returns online.
Sometimes, people confuse digital signatures with electronic signatures. An electronic signature is a wider term for any electronic data that acts like a signature. But not all electronic signatures use the strong security of digital signatures. In some places, like the United States and the European Union, electronic signatures can be legally binding. In India, digital signatures have legal validity, but other electronic signatures do not.
How Digital Signatures Work
A digital signature system usually has two main parts that work together:
- A signing process takes your message and your secret private key to create a unique digital signature.
- A verifying process uses the message, the digital signature, and your public key (which is shared with others) to check if the signature is real and if the message hasn't been changed.
For a digital signature system to be good, it needs two important things:
- A signature made with a specific message and private key must always be accepted when checked with that message and the matching public key.
- It should be almost impossible for someone who doesn't have your private key to create a valid signature for your messages.
Keeping Digital Signatures Safe
Making sure digital signatures are secure is very important. In 1984, three smart people named Shafi Goldwasser, Silvio Micali, and Ron Rivest figured out how to define how secure a digital signature should be. They also created a system called the GMR signature scheme. This system was designed to be very strong, even if an attacker tried to get many signatures from you.
Goldwasser, Micali, and Rivest also described different ways attackers might try to break digital signatures:
- In a key-only attack, the attacker only has your public key.
- In a known message attack, the attacker has some valid signatures for messages they know about, but they didn't choose those messages.
- In an adaptive chosen message attack, the attacker can choose any messages they want and get you to sign them. This is the hardest attack to defend against.
They also explained what an attacker might try to achieve:
- A total break means the attacker finds your secret signing key.
- A universal forgery means the attacker can create a valid signature for any message.
- A selective forgery means the attacker can create a valid signature for a specific message they chose.
- An existential forgery means the attacker can create just one new valid message and signature pair that wasn't known before.
The strongest kind of security for digital signatures means they can protect against even the toughest attacks, like an existential forgery under an adaptive chosen message attack.
Related pages
See also
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In Spanish: Firma digital para niños
