RFC 8032: Avoid unnecessary doublings in precomputation

peterdettman · peterdettman · commit 04e57f9ff6d5 · 2018-09-25T21:55:19.000+07:00
diff --git a/crypto/src/math/ec/rfc8032/Ed25519.cs b/crypto/src/math/ec/rfc8032/Ed25519.cs
@@ -670,9 +670,12 @@ public static void Precompute()
 
                     ds[t] = PointCopy(p);
 
-                    for (int s = 1; s < PrecompSpacing; ++s)
+                    if (b + t != PrecompBlocks + PrecompTeeth - 2)
                     {
-                        PointDouble(p);
+                        for (int s = 1; s < PrecompSpacing; ++s)
+                        {
+                            PointDouble(p);
+                        }
                     }
                 }
 
diff --git a/crypto/src/math/ec/rfc8032/Ed448.cs b/crypto/src/math/ec/rfc8032/Ed448.cs
@@ -622,9 +622,12 @@ public static void Precompute()
 
                     ds[t] = PointCopy(p);
 
-                    for (int s = 1; s < PrecompSpacing; ++s)
+                    if (b + t != PrecompBlocks + PrecompTeeth - 2)
                     {
-                        PointDouble(p);
+                        for (int s = 1; s < PrecompSpacing; ++s)
+                        {
+                            PointDouble(p);
+                        }
                     }
                 }
 

Original file line number	Diff line number	Diff line change
`@@ -670,9 +670,12 @@ public static void Precompute()`
`670`	`670`
`671`	`671`	`ds[t] = PointCopy(p);`
`672`	`672`
`673`		`- for (int s = 1; s < PrecompSpacing; ++s)`
	`673`	`+ if (b + t != PrecompBlocks + PrecompTeeth - 2)`
`674`	`674`	`{`
`675`		`- PointDouble(p);`
	`675`	`+ for (int s = 1; s < PrecompSpacing; ++s)`
	`676`	`+ {`
	`677`	`+ PointDouble(p);`
	`678`	`+ }`
`676`	`679`	`}`
`677`	`680`	`}`
`678`	`681`
Original file line number	Diff line number	Diff line change
`@@ -622,9 +622,12 @@ public static void Precompute()`
`622`	`622`
`623`	`623`	`ds[t] = PointCopy(p);`
`624`	`624`
`625`		`- for (int s = 1; s < PrecompSpacing; ++s)`
	`625`	`+ if (b + t != PrecompBlocks + PrecompTeeth - 2)`
`626`	`626`	`{`
`627`		`- PointDouble(p);`
	`627`	`+ for (int s = 1; s < PrecompSpacing; ++s)`
	`628`	`+ {`
	`629`	`+ PointDouble(p);`
	`630`	`+ }`
`628`	`631`	`}`
`629`	`632`	`}`
`630`	`633`