What Algorithm Is Used to Sign a Bitcoin Transaction?

Elliptic Curve Digital Signature Algorithm (ECDSA) secp256k1 is used to sign the transaction.

This algorithm has two main functions:

a. Sign Function:

Signature = Sign(Transaction Hash, Private Key)

This function is used to create the digital signature.

b. Verify Function:

Verify(Transaction Hash, Signature, Public Key)

This function is used to verify the digital signature.