# HG changeset patch
# User Laman
# Date 2017-09-17 19:29:37
# Node ID 438dcebc9c63518767709e1e64b6ab43c36c70ff
# Parent  86a5417085efabb0391c8205f0d1f1fa725e6396

splitting the secret

diff --git a/src/gf256.py b/src/gf256.py
--- a/src/gf256.py
+++ b/src/gf256.py
@@ -26,3 +26,12 @@ def ffmul(a, b):
 	t=L[a]+L[b]
 	if t>255: t-=255
 	return E[t]
+
+
+def evaluate(coefs,x):
+	res=0
+	xK=1
+	for a in coefs:
+		res^=ffmul(a,xK)
+		xK=ffmul(xK,x)
+	return res
diff --git a/src/shamira.py b/src/shamira.py
new file mode 100644
--- /dev/null
+++ b/src/shamira.py
@@ -0,0 +1,18 @@
+import os
+
+import gf256
+
+
+def shareByte(secretB,k,n):
+	assert n<255
+	coefs=[int(secretB)]+[int(b) for b in os.urandom(k-1)]
+	points=[gf256.evaluate(coefs,i) for i in range(1,n+1)]
+	return points
+
+
+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))