ed25519: Fix carry bug

dchest · dchest · commit 8ad6b7ef6993 · 2020-02-10T20:50:41.000+01:00
See dchest/tweetnacl-js#187
diff --git a/packages/ed25519/ed25519.ts b/packages/ed25519/ed25519.ts
@@ -704,7 +704,7 @@ function modL(r: Uint8Array, x: Float64Array) {
         carry = 0;
         for (j = i - 32, k = i - 12; j < k; ++j) {
             x[j] += carry - 16 * x[i] * L[j - (i - 32)];
-            carry = (x[j] + 128) >> 8;
+            carry = Math.floor((x[j] + 128) / 256);
             x[j] -= carry * 256;
         }
         x[j] += carry;

Original file line number	Diff line number	Diff line change
`@@ -704,7 +704,7 @@ function modL(r: Uint8Array, x: Float64Array) {`
`704`	`704`	`carry = 0;`
`705`	`705`	`for (j = i - 32, k = i - 12; j < k; ++j) {`
`706`	`706`	`x[j] += carry - 16 * x[i] * L[j - (i - 32)];`
`707`		`- carry = (x[j] + 128) >> 8;`
	`707`	`+ carry = Math.floor((x[j] + 128) / 256);`
`708`	`708`	`x[j] -= carry * 256;`
`709`	`709`	`}`
`710`	`710`	`x[j] += carry;`