Explanation about digital signature

[Dzwaafu11]

I came across something today while doing some research. I came across something called "digital signature," which I do not understand and need more explanation on that, please.
 
What is this digital signature all about, and what is it used for in bitcoin technology?
 
And if I want to use this digital signature, where can I use it, or what will I do in bitcoin technology that will require me to use a digital signature? And then how does a digital signature work?
 
Thank you all; all answers will be appreciated.

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[Zaguru12]

In a simple explanation;
Let’s say you have a public key and you are asked to prove the ownership of this key or even an address, you can just give them the digital signature in place of the private key for ownership prove.

The digital signature is a number derived from a private key so there is no way you can have a digital signature without the private key. So presenting it simply means you hold the private key to that wallet.

The digital signature is used to spend your output without having to reveal your private key. It is unique since it differs in every transaction. So no two transactions can have the same signature. It is created by combining both the private key with the transaction data.

Check https://learnmeabitcoin.com/beginners/digital_signatures

[ranochigo]

Asymmetric Cryptography, for example RSA, ECDSA function by having a public key and a private key pair. Using the private key, you can create a signature that can be verified by using the public key and the signature and thereby proving that you have knowledge of the private key. Signatures are used in transactions and message signing for Bitcoin. In a transaction, there are address schemes (P2PKH, P2WPKH, etc) which requires the transactions to be signed with a signature and the public key being provided. Using the public key and the signature, nodes can check that the signature is signed with the correct keypair and that it corresponds to the redeem script of the output.

In message signing, it is usually done to prove ownership of an address but that is fairly debatable. Having a signature and a message that checks out merely means that whoever that has knowledge of the corresponding private key has explicitly signed the contents of that message.

PGP is an alternate application of asymmetric cryptography.

[Nheer]

Since your private key is intended to remain secret and not be known by anyone else, the digital signature acts more as a stand-in for your private key when proving ownership rather than displaying your private key to everyone on the network.

[Stalker22]

What is this digital signature all about, and what is it used for in bitcoin technology?
~

When you make a transaction on the Bitcoin network, your wallet software puts a digital signature on the transaction data. This signature proves that you own the private key used to authorize the transaction, making it valid. Without this signature, transactions would not be accepted by the nodes on the network.

[Accardo]

And if I want to use this digital signature, where can I use it, or what will I do in bitcoin technology that will require me to use a digital signature?

Using digital signature depends on the type of transaction you want to place, which is grouped under the different types of SIGHASH_FLAG; this is a single byte that determines what data is required before a transaction is seen as valid. There are about 3 valid SIGHASH_FLAGs available for bitcoin transaction. Like suggested above most wallets use the P2PKH scripts embedded with a SIGHASH_ALL Flags, which insists that all inputs and outputs must remain unchanged before the transaction will be considered as valid.

On the other flip, what you'll do that'll require you to use a digital signature can fall upon if you want to build a software that requires the security of data, or if you want to perform a transaction that requires crowdfunding you can use a SIGHASH_ALL/ANYONECANPAY FLAG appropriate to it, whereby the transaction won't be valid until the targeted amount of money is reached. Moving ahead, you'll be the one to construct them into your software to suit your need and you'll need to know the mathematics behind ECDSA.

And then how does a digital signature work?

Two things to understand about digital signature, due to security issues, digital signature works in both ways to keep the private keys secure like shown below, PGP is an alternative to PKI. They both work differently, PKI requires a third party Certificate authority to validate the public keys and verify their private keys, while the Pretty Good Privacy algorithm uses asymmetric cryptography; requires both private and public key encryption and authentication. Hence digital signature is not only used for bitcoin transaction, different bodies use it for different reasons.

PGP is an alternate application of asymmetric cryptography.

[citb0in]

What is this digital signature all about, and what is it used for in bitcoin technology?
And if I want to use this digital signature, where can I use it, or what will I do in bitcoin technology that will require me to use a digital signature? And then how does a digital signature work?

see if this helps

https://www.bitcoin.com/get-started/how-bitcoin-transactions-work/
https://www.coinbase.com/cloud/discover/dev-foundations/digital-signatures
https://academy.binance.com/en/articles/what-is-a-digital-signature
https://learnmeabitcoin.com/beginners/digital_signatures

[Amphenomenon]

What is this digital signature all about, and what is it used for in bitcoin technology?
 
And if I want to use this digital signature, where can I use it, or what will I do in bitcoin technology that will require me to use a digital signature? And then how does a digital signature work?

 Digital signature is similar to paper signature in that it is use to sign transaction/document but the thing about this digital signature is that it is made in way that someone cannot sign a new signature from previous messages signed without the private key, the private key allow the owner to sign transaction which contain a message and a public key, so that the transaction can be verify by anyone.

Three operations for generating a digital signature are :
1. The generate keys which contain the private and public key
2. The sign operation by which the message is signed with the private key
3. the verification operation to verify if the  message, private key and public key are valid

[Flexystar]

Asymmetric Cryptography, for example RSA, ECDSA function by having a public key and a private key pair. Using the private key, you can create a signature that can be verified by using the public key and the signature and thereby proving that you have knowledge of the private key. Signatures are used in transactions and message signing for Bitcoin. In a transaction, there are address schemes (P2PKH, P2WPKH, etc) which requires the transactions to be signed with a signature and the public key being provided. Using the public key and the signature, nodes can check that the signature is signed with the correct keypair and that it corresponds to the redeem script of the output.

In message signing, it is usually done to prove ownership of an address but that is fairly debatable. Having a signature and a message that checks out merely means that whoever that has knowledge of the corresponding private key has explicitly signed the contents of that message.

PGP is an alternate application of asymmetric cryptography.

Amazing mechanism made by cryptographer. I am not sure if this is associates with the same Cryptograph invention that dates back to the Swedish company in 1916 or not but if yes then people had astounding mind and work back in the time. I think if the theory is right then Mr. Satoshi made use of these research papers to give rise to what we call blockchain today and then everything else is the present that we live with.

I read the full explanation of crypto signatures in vast detail after visiting this thread only otherwise I was only signing the messages now and then for various confidentiality agreements with few vendors. All you I used to do is sign a message and circulate tot he party and they used to put in their electrum and verify for the authenticity.

It's cool that it is always synched up wherever you create it and wherever you verify it. For me it's like "KEY & LOCK" in simplest explanation.

[Prancheiro]

What is this digital signature all about, and what is it used for in bitcoin technology?
 

What helped me understand the concept was first understand Electronic Signatures and what problems Digital Signatures solve.

Most of us engage with electronic signatures, often without realizing it. Here are some commonplace examples:

- Agreeing to the terms and conditions of a software or online service by clicking "I Accept."
- Signing on digital pads after credit card transactions at retail outlets.
- Using signing platforms, where one can draw or upload an image of your signature to digitally sign a document.

The problem with electronic signatures is that they rely on a trusted third party to validate the authenticity of the signatory and the integrity of the signed data. For instance, when using e-signature platforms, the platform itself acts as the third party, ensuring that the signatory is who they claim to be and that the document hasn't been tampered with after signing.

In Bitcoin, who will guarantee that a signature is valid?

That's where digital signatures come in:

Digital Signature:

It is a specific type of electronic signature. Rooted in cryptography, it involves creating a unique digital code (or 'signature') using a private cryptographic key. When others receive the digitally signed document, they can use the signatory's public cryptographic key to verify the document's authenticity and ensure it remains unaltered since being signed.

A digital signature is created by taking the message you want to sign and applying a mathematical formula with your private key. Anyone who knows your public key can mathematically verify that this signature was indeed created by the holder of the associated private key (but without knowing the private key itself).

They guarantee:

- Authentication (Proves that the the sender is the one who sent the message/transaction);
- Integrity (proves the message/transaction was not modified in transit);

Hope this can help!

[jvanname]

The easiest digital signature algorithm to understand is probably Lamport's one time signature algorithm since this algorithm is based on cryptographic hash functions. Of course, Lamport's one time signature is only good for signing one document, but Ralph Merkle has generalized this signature scheme so that one can sign multiple documents with just one private-public key pair with the help of Merkle trees (Merkle signature scheme).

[NotATether]

It's important to note that digital signatures are not only used in sign message. They are also used each time you create a transaction, because the other nodes on the network need to be able to verify it was your public key which had created the transaction, and not someone else's. That's what is done when you sign a transaction using a wallet - most of them abstract this to the part where you have to enter a password to create a transaction.