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Bug calculation carry/borrow when right=0xFFFFFFFF and carry/borrow=1 #227

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valencif wants to merge 1 commit into kmackay:master from valencif:master

+2 −6

valencif commented Jun 7, 2024

Bug in uECC_vli_add and uECC_vli_sub

Error appear when oper2 = 0xFFFFFFFF and previous carry=1

i.e with 8 bits:

oper1:       83 +
oper2:       FF
           ------
   F+3=      12
 1+8+F=     18   // carry = (sum < left[i])  -->  carry = (8<8)  --> carry = 0 (Incorrect)
           ------
            182  //  Correct result

Equivalent error appears in the calculation of borrow in uECC_vli_sub


          Fix calculation of carry/borrow when right=0xFFFFFFFF and carry/borro…

af55a0f

…w = 1

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