<html><body><span class="xfm_19758312">
Hi all!<br/>Please advise on this protocol:<br/><br/>Two parties comparing 2 bytes short common secret using EC25519 (only mul and mul_base procedures) and SHA3 hash.<br/>Any side can be active adversary trying obtain secret.<br/><br/>c = H(secret)<br/><br/>Side A:<br/>- picks a at random<br/>- computes A = mul_base(a)<br/>- computes A' = mul(c, A)<br/>- sends A' to side B<br/><br/>Side B:<br/>- picks b at random<br/>- computes B = mul_base(b)<br/>- computes B' = mul(c, B)<br/>- sends B' to side A<br/><br/>Side A:<br/>- computes S = mul(a, B')<br/>- sends MB=H(A' | B' | S) to side A<br/><br/>Side B:<br/>- computes S= mul(b, A')<br/>- sends MA=H(B' | A' | S) to side B<br/><br/>Both A and B checks MA and MB.<br/><br/>Is this protocol safe?<br/></span></body></html>