Some ECC Types and Operations

Prof Bill Buchanan OBE FRSE
2 min readApr 5, 2021

We have a number of possible types of elliptic curve methods. These have a field (the prime number used), the order (the number of elliptic curve points), an a value, a b value, and a generator point (G). For a Weierstrass curve the standard form is y²=x³+ax+b (such as secp256k1). With a twisted Edwards curve (such as Ed25519) we have the form of ax²+y²=1+dx²y². A Montgomery curve has the form of by²=x³+ax²+x.

With ECC, we typically take a base point (G) and multiply it with our private key (sk), and then generate our public key point (sk.G). A sample run for secp256k1 and for 1,000G is [here]:

Curve: secp256k1
====================
G: (0x79be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798 , 0x483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8)
Bit size: 256
Order: 115792089237316195423570985008687907852837564279074904382605163141518161494337
Field: 115792089237316195423570985008687907853269984665640564039457584007908834671663
a: 0
b: 7
====================
1000G: (0x4a5169f673aa632f538aaa128b6348536db2b637fd89073d49b6a23879cdb3ad , 0xbaf1e702eb2a8badae14ba09a26a8ca7cb1127b64b2c39a1c7ba61f4a3c62601)Point add (add 1G on)1001G: (0x9d1abaec9f5715a15c7628244170951e0f85e87f68ca5393d3f9fc3fa23a69c8 , 0xf21ee70050dbb61c238c89e62942353871b010e798867bdd149ad28b3f28cadf)

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Prof Bill Buchanan OBE FRSE

Professor of Cryptography. Serial innovator. Believer in fairness, justice & freedom. Based in Edinburgh. Old World Breaker. New World Creator. Building trust.