Blockchain + Digital Signature

A distributed register can be used to store static records and/or dynamic transaction data without central coordination by using a consensus-based mechanism to check the validity of transactions. A blockchain is a distributed database that maintains a continuously growing list of data records that cannot be tampered with.

Blockchain is a public ledger of all transactions made with Bitcoin and is meant to replace an external, trusted third-party certificate authority while also preventing anyone from being able to go backward and cover their tracks if they corrupted an entry.

The technology works on the following properties:

1. Log replication: To create resiliency, log-based replication is increasingly used for distributed systems to replicate logs to all peers in the network.

2. Provable value chain: The values stored in the blockchain can be digital currency (such as the widely known Bitcoin), data, documents, and other assets. Hash chains are kept for each block, providing a history of changes, which helps protect data integrity of the block asset.

3. Public-key cryptography: Blockchain uses different types of cryptography, including ECDSA and elliptic curve to authenticate transactions.

4. Decentralized transaction ledger: The ledger is blockchain and is maintained without a central authority — and acts as a decentralized reconciliation system.

Blockchain with digital signatures has become a key control in many organizations' security strategies, relying on the use of certificates and complex mathematical algorithms to provide authenticity of the data and protection against forgery.

But suppose a company wants to accept Bitcoins for its trades. Now, because of security reasons, the company would not want a single employee to have access to the company’s Bitcoin wallet’s password. Any transaction should need approval from more than one employee of the company. A multisignature address is created for that purpose.

A multisignature address is an address associated with more than one ECDSA private keys. So, in an m-of-n address, when a Bitcoin address is generated, it is associated with n private keys. And, at least m private keys will be required to make a transaction possible.

And this concept can be used in making digital signatures. One can create a multisignature m-of-n address using n private keys and use that to record digital signature of documents in a blockchain. Anyone can verify the digital signature using public keys, but to make the digital signature one would need at least m private keys, out of n private keys associated with the multisignature address. By using private keys between the signer and the recipient, data transactions can be maintained by only approved parties.