EC Cryptography Tutorials - Herong's Tutorial Examples - v1.00, by Dr. Herong Yang
Is ECDH Key Exchange Secure
This section discusses the question of: how secure is the ECDH (Elliptic Curve Diffie-Hellman) key exchange protocol?
Is ECDH Key Exchange Protocol Secure? Yes, ECDH Key Exchange protocol is secure, if both Alice and Bob select large private numbers, i and j.
If Eve gets a copy of QA and QB by taking copies of messages exchanged between Alice and Bob, Eve needs to perform the reverse operation to find dA, such that dA*G = QA; or to find dB, such that dB*G = QB.
If dA and dB are both 256-bit integers, Eve needs to perform about 2256 operations. That is about 1.2239143543602674e+60 years on a laptop with a 3 GHZ CPU doing 1 operation per CPU click.
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