Changeset - db65075fe7e0
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Laman - 7 years ago 2017-09-17 22:36:32

reconstructing the secret
2 files changed with 21 insertions and 1 deletions:
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src/gf256.py
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@@ -32,6 +32,19 @@ def evaluate(coefs,x):
 
	res=0
 
	xK=1
 
	for a in coefs:
 
		res^=ffmul(a,xK)
 
		xK=ffmul(xK,x)
 
	return res
 

	
 

	
 
def getConstantCoef(k,*points):
 
	res=0
 
	for i in range(k):
 
		(x,y)=points[i]
 
		prod=1
 
		for j in range(k):
 
			if i==j: continue
 
			(xj,yj)=points[j]
 
			prod=ffmul(prod, (ffmul(xj,inv[xj^x])))
 
		res^=ffmul(y,prod)
 
	return res
src/shamira.py
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@@ -12,7 +12,14 @@ def shareByte(secretB,k,n):
 

	
 
def generate(secret,k,n):
 
	shares=[shareByte(b,k,n) for b in secret]
 
	return [(i+1, [s[i] for s in shares]) for i in range(n)]
 

	
 

	
 
print(generate(b"key",2,3))
 
def reconstruct(*shares):
 
	k=len(shares)
 
	secretLen=len(shares[0][1])
 
	res=[None]*secretLen
 
	for i in range(secretLen):
 
		bs=[(x,s[i]) for (x,s) in shares]
 
		res[i]=(gf256.getConstantCoef(k,*bs))
 
	return bytes(res)
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