From 73a1417859e1251a93e7157a137ca0d220beb2b2 Mon Sep 17 00:00:00 2001
From: siddharth ravikumar <s@ricketyspace.net>
Date: Sun, 14 Aug 2022 14:28:52 -0400
Subject: lib: remove `egcd`

No longer needed.
---
 lib/rsa.go      | 48 ------------------------------------------------
 lib/rsa_test.go | 43 -------------------------------------------
 2 files changed, 91 deletions(-)

diff --git a/lib/rsa.go b/lib/rsa.go
index 3d29bae..1a860eb 100644
--- a/lib/rsa.go
+++ b/lib/rsa.go
@@ -8,12 +8,6 @@ import (
 	"math/big"
 )
 
-type GCDResult struct {
-	Gcd *big.Int
-	X   *big.Int // Bézout coefficient 'x'
-	Y   *big.Int // Bézout coefficient 'y'
-}
-
 // Represents an RSA key pair.
 type RSAPair struct {
 	Public  *RSAPub
@@ -39,48 +33,6 @@ func biCopy(a, b *big.Int) *big.Int {
 	return a
 }
 
-// Extended Euclidian.
-func egcd(a, b *big.Int) GCDResult {
-	// Initialize.
-	s0 := big.NewInt(1)
-	s1 := big.NewInt(0)
-	r0 := biCopy(big.NewInt(0), a)
-	r1 := biCopy(big.NewInt(0), b)
-
-	for r1.Cmp(big.NewInt(0)) != 0 {
-		q := big.NewInt(0)
-		q.Div(r0, r1)
-
-		tr := big.NewInt(0)
-		tr = tr.Mul(q, r1)
-		tr = tr.Sub(r0, tr)
-
-		biCopy(r0, r1)
-		biCopy(r1, tr)
-
-		tr = big.NewInt(0)
-		tr = tr.Mul(q, s1)
-		tr = tr.Sub(s0, tr)
-
-		biCopy(s0, s1)
-		biCopy(s1, tr)
-	}
-
-	x := biCopy(big.NewInt(0), s0)
-	y := big.NewInt(0)
-	if b.Cmp(big.NewInt(0)) != 0 {
-		y = y.Mul(s0, a)
-		y = y.Sub(r0, y)
-		y = y.Div(y, b)
-	}
-
-	return GCDResult{
-		Gcd: biCopy(big.NewInt(0), r0),
-		X:   x,
-		Y:   y,
-	}
-}
-
 func invmod(a, n *big.Int) (*big.Int, error) {
 	// Initialize.
 	t0 := big.NewInt(0)
diff --git a/lib/rsa_test.go b/lib/rsa_test.go
index c0d4ce4..eee20c6 100644
--- a/lib/rsa_test.go
+++ b/lib/rsa_test.go
@@ -8,49 +8,6 @@ import (
 	"testing"
 )
 
-func TestEGCD(t *testing.T) {
-	a := big.NewInt(128)
-	b := big.NewInt(96)
-	r := egcd(a, b)
-	if r.Gcd.Cmp(big.NewInt(32)) != 0 {
-		t.Errorf("gcd(128, 96) != 32")
-	}
-	if r.X.Cmp(big.NewInt(1)) != 0 || r.Y.Cmp(big.NewInt(-1)) != 0 {
-		t.Errorf("bézout_coef(128, 96) != {1,-1}")
-	}
-
-	a = big.NewInt(360)
-	b = big.NewInt(210)
-	r = egcd(a, b)
-	if r.Gcd.Cmp(big.NewInt(30)) != 0 {
-		t.Errorf("gcd(360, 210) != 30")
-	}
-	if r.X.Cmp(big.NewInt(3)) != 0 || r.Y.Cmp(big.NewInt(-5)) != 0 {
-		t.Errorf("bézout_coef(360, 210) != {3,-5}")
-	}
-
-	a = big.NewInt(108)
-	b = big.NewInt(144)
-	r = egcd(a, b)
-	if r.Gcd.Cmp(big.NewInt(36)) != 0 {
-		t.Errorf("gcd(108, 144) != 36")
-	}
-	if r.X.Cmp(big.NewInt(-1)) != 0 || r.Y.Cmp(big.NewInt(1)) != 0 {
-		t.Errorf("bézout_coef(108, 144) != {-1,1}")
-	}
-
-	a = big.NewInt(240)
-	b = big.NewInt(46)
-	r = egcd(a, b)
-	if r.Gcd.Cmp(big.NewInt(2)) != 0 {
-		t.Errorf("gcd(240, 46) != 2")
-	}
-	if r.X.Cmp(big.NewInt(-9)) != 0 || r.Y.Cmp(big.NewInt(47)) != 0 {
-		t.Errorf("bézout_coef(240, 46) != {-9,47}")
-	}
-
-}
-
 func TestInvMod(t *testing.T) {
 	a := big.NewInt(17)
 	b := big.NewInt(3120)
-- 
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