To generate an ECDSA signature, you first calculate the hash of the message using a cryptographic hash function like SHA-256. Then, you randomly select a number k in the range [1…n-1], where n is the order of the elliptic curve’s subgroup generated by its generator point G. You then compute the point R = k * G and take its x-coordinate. Finally, you calculate the signature proof s as follows:
s = (k^-1) * ((h + r * privKey) mod n)
where h is the hash of the message, r is the x-coordinate of point R, and privKey is your private key. The calculated signature {r, s} consists of two integers.
To verify an ECDSA signature, you first calculate the hash of the message using the same cryptographic hash function as before. Then, you compute the point R’ = (pubKey * h) mod n and take its x-coordinate. Finally, you check if s is equal to ((k^-1) * (h + r’ * privKey)) mod n, where pubKey is the public key corresponding to your private key used for signing. If it is, then the signature is valid; otherwise, it is invalid.
ECDSA has several advantages over traditional digital signature algorithms like RSA and DSA: it uses smaller keys (which makes it faster), it provides better security against side-channel attacks, and it can be implemented more efficiently on hardware devices such as smart cards or embedded systems. However, ECDSA also has some disadvantages, including the fact that its security is based on elliptic curves rather than prime factorization, which means that there are fewer mathematical tools available for analyzing its properties.
In terms of implementation, ECDSA can be used with various elliptic curve parameters and cryptographic hash functions to provide different levels of security and performance. For example, the secp256k1 curve is commonly used in Bitcoin and other blockchain systems due to its high level of security and efficient implementation on hardware devices like ASICs or GPUs.