10.17 The following is a first attempt at an Elliptic Curve signature scheme. We have a global elliptic curve, prime p,and "generator" G. Alice picks a private signing key XA and forms the public verifying key YA = XAG. To sign a message M: Alice picks a value k. Alice sends Bob M, k and the signature S = M kXAG. Bob verifies that M = S + kYA a. Show that this scheme works. That is, show that the verification process produces an equality if the signature is valid. b. Show that the scheme is unacceptable by describing a simple technique for forging a user"s signature on an arbitrary message. | |
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