diff --git a/lib/std/crypto/25519/ed25519.zig b/lib/std/crypto/25519/ed25519.zig
index 6874d5a394..e7df807cd3 100644
--- a/lib/std/crypto/25519/ed25519.zig
+++ b/lib/std/crypto/25519/ed25519.zig
@@ -144,7 +144,7 @@ pub const Ed25519 = struct {
             a_batch[i] = a;
         }
 
-        var hram_batch: [count]Curve.scalar.Scalar = undefined;
+        var hram_batch: [count]Curve.scalar.CompressedScalar = undefined;
         for (signature_batch) |signature, i| {
             var h = Sha512.init(.{});
             h.update(&r_batch[i]);
@@ -155,7 +155,7 @@ pub const Ed25519 = struct {
             hram_batch[i] = Curve.scalar.reduce64(hram64);
         }
 
-        var z_batch: [count]Curve.scalar.Scalar = undefined;
+        var z_batch: [count]Curve.scalar.CompressedScalar = undefined;
         for (z_batch) |*z| {
             try std.crypto.randomBytes(z[0..16]);
             mem.set(u8, z[16..], 0);
diff --git a/lib/std/crypto/25519/scalar.zig b/lib/std/crypto/25519/scalar.zig
index e9f46d68b9..c5e460d29e 100644
--- a/lib/std/crypto/25519/scalar.zig
+++ b/lib/std/crypto/25519/scalar.zig
@@ -6,129 +6,17 @@
 const std = @import("std");
 const mem = std.mem;
 
-/// A 32-byte representation of a scalar in 0 .. 2^252 + 27742317777372353535851937790883648493
-pub const Scalar = [32]u8;
-
 /// 2^252 + 27742317777372353535851937790883648493
 pub const field_size = [32]u8{
     0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58, 0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, // 2^252+27742317777372353535851937790883648493
 };
 
+/// A compressed scalar
+pub const CompressedScalar = [32]u8;
+
 /// Zero
 pub const zero = [_]u8{0} ** 32;
 
-/// Double-word scalar representation
-const ScalarExpanded = struct {
-    limbs: [64]i64 = [_]i64{0} ** 64,
-
-    fn fromBytes(s: [32]u8) ScalarExpanded {
-        var limbs: [64]i64 = undefined;
-        for (s) |x, idx| {
-            limbs[idx] = @as(i64, x);
-        }
-        mem.set(i64, limbs[32..], 0);
-        return .{ .limbs = limbs };
-    }
-
-    fn fromBytes64(s: [64]u8) ScalarExpanded {
-        var limbs: [64]i64 = undefined;
-        for (s) |x, idx| {
-            limbs[idx] = @as(i64, x);
-        }
-        return .{ .limbs = limbs };
-    }
-
-    fn reduce(e: *ScalarExpanded) void {
-        const limbs = &e.limbs;
-        var carry: i64 = undefined;
-        var i: usize = 63;
-        while (i >= 32) : (i -= 1) {
-            carry = 0;
-            const k = i - 12;
-            const xi = limbs[i];
-            var j = i - 32;
-            while (j < k) : (j += 1) {
-                const xj = limbs[j] + carry - 16 * xi * @as(i64, field_size[j - (i - 32)]);
-                carry = (xj + 128) >> 8;
-                limbs[j] = xj - carry * 256;
-            }
-            limbs[k] += carry;
-            limbs[i] = 0;
-        }
-        carry = 0;
-        comptime var j: usize = 0;
-        inline while (j < 32) : (j += 1) {
-            const xi = limbs[j] + carry - (limbs[31] >> 4) * @as(i64, field_size[j]);
-            carry = xi >> 8;
-            limbs[j] = xi & 255;
-        }
-        j = 0;
-        inline while (j < 32) : (j += 1) {
-            limbs[j] -= carry * @as(i64, field_size[j]);
-        }
-        j = 0;
-        inline while (j < 32) : (j += 1) {
-            limbs[j + 1] += limbs[j] >> 8;
-        }
-        j = 0;
-        inline while (j < 32) : (j += 1) {
-            limbs[j] &= 0xff;
-        }
-        limbs[32] = 0;
-    }
-
-    fn toBytes(e: *ScalarExpanded) [32]u8 {
-        e.reduce();
-        var r: [32]u8 = undefined;
-        var i: usize = 0;
-        while (i < 32) : (i += 1) {
-            r[i] = @intCast(u8, e.limbs[i]);
-        }
-        return r;
-    }
-
-    fn add(a: ScalarExpanded, b: ScalarExpanded) ScalarExpanded {
-        var r = ScalarExpanded{};
-        comptime var i = 0;
-        inline while (i < 64) : (i += 1) {
-            r.limbs[i] = a.limbs[i] + b.limbs[i];
-        }
-        return r;
-    }
-
-    fn mul(a: ScalarExpanded, b: ScalarExpanded) ScalarExpanded {
-        var r = ScalarExpanded{};
-        var i: usize = 0;
-        while (i < 32) : (i += 1) {
-            const ai = a.limbs[i];
-            comptime var j = 0;
-            inline while (j < 32) : (j += 1) {
-                r.limbs[i + j] += ai * b.limbs[j];
-            }
-        }
-        r.reduce();
-        return r;
-    }
-
-    fn sq(a: ScalarExpanded) ScalarExpanded {
-        return a.mul(a);
-    }
-
-    fn mulAdd(a: ScalarExpanded, b: ScalarExpanded, c: ScalarExpanded) ScalarExpanded {
-        var r: ScalarExpanded = .{ .limbs = c.limbs };
-        var i: usize = 0;
-        while (i < 32) : (i += 1) {
-            const ai = a.limbs[i];
-            comptime var j = 0;
-            inline while (j < 32) : (j += 1) {
-                r.limbs[i + j] += ai * b.limbs[j];
-            }
-        }
-        r.reduce();
-        return r;
-    }
-};
-
 /// Reject a scalar whose encoding is not canonical.
 pub fn rejectNonCanonical(s: [32]u8) !void {
     var c: u8 = 0;
@@ -148,12 +36,12 @@ pub fn rejectNonCanonical(s: [32]u8) !void {
 
 /// Reduce a scalar to the field size.
 pub fn reduce(s: [32]u8) [32]u8 {
-    return ScalarExpanded.fromBytes(s).toBytes();
+    return Scalar.fromBytes(s).toBytes();
 }
 
 /// Reduce a 64-bytes scalar to the field size.
 pub fn reduce64(s: [64]u8) [32]u8 {
-    return ScalarExpanded.fromBytes64(s).toBytes();
+    return ScalarDouble.fromBytes64(s).toBytes();
 }
 
 /// Perform the X25519 "clamping" operation.
@@ -165,17 +53,17 @@ pub inline fn clamp(s: *[32]u8) void {
 
 /// Return a*b (mod L)
 pub fn mul(a: [32]u8, b: [32]u8) [32]u8 {
-    return ScalarExpanded.fromBytes(a).mul(ScalarExpanded.fromBytes(b)).toBytes();
+    return Scalar.fromBytes(a).mul(Scalar.fromBytes(b)).toBytes();
 }
 
 /// Return a*b+c (mod L)
 pub fn mulAdd(a: [32]u8, b: [32]u8, c: [32]u8) [32]u8 {
-    return ScalarExpanded.fromBytes(a).mulAdd(ScalarExpanded.fromBytes(b), ScalarExpanded.fromBytes(c)).toBytes();
+    return Scalar.fromBytes(a).mul(Scalar.fromBytes(b)).add(Scalar.fromBytes(c)).toBytes();
 }
 
 /// Return a*8 (mod L)
 pub fn mul8(s: [32]u8) [32]u8 {
-    var x = ScalarExpanded.fromBytes(s);
+    var x = Scalar.fromBytes(s);
     x = x.add(x);
     x = x.add(x);
     x = x.add(x);
@@ -184,7 +72,7 @@ pub fn mul8(s: [32]u8) [32]u8 {
 
 /// Return a+b (mod L)
 pub fn add(a: [32]u8, b: [32]u8) [32]u8 {
-    return ScalarExpanded.fromBytes(a).add(ScalarExpanded.fromBytes(b)).toBytes();
+    return Scalar.fromBytes(a).add(Scalar.fromBytes(b)).toBytes();
 }
 
 /// Return -s (mod L)
@@ -208,9 +96,678 @@ pub fn sub(a: [32]u8, b: [32]u8) [32]u8 {
     return add(a, neg(b));
 }
 
+/// A scalar in unpacked reprentation
+pub const Scalar = struct {
+    const Limbs = [5]u64;
+    limbs: Limbs = undefined,
+
+    /// Unpack a 32-byte representation of a scalar
+    pub fn fromBytes(bytes: [32]u8) Scalar {
+        return ScalarDouble.fromBytes32(bytes).reduce(5);
+    }
+
+    /// Pack a scalar into bytes
+    pub fn toBytes(expanded: *const Scalar) [32]u8 {
+        var bytes: [32]u8 = undefined;
+        var i: usize = 0;
+        while (i < 4) : (i += 1) {
+            mem.writeIntLittle(u64, bytes[i * 7 ..][0..8], expanded.limbs[i]);
+        }
+        mem.writeIntLittle(u32, bytes[i * 7 ..][0..4], @intCast(u32, expanded.limbs[i]));
+        return bytes;
+    }
+
+    /// Return x+y (mod l)
+    pub fn add(x: Scalar, y: Scalar) Scalar {
+        const carry0 = (x.limbs[0] + y.limbs[0]) >> 56;
+        const t0 = (x.limbs[0] + y.limbs[0]) & 0xffffffffffffff;
+        const t00 = t0;
+        const c0 = carry0;
+        const carry1 = (x.limbs[1] + y.limbs[1] + c0) >> 56;
+        const t1 = (x.limbs[1] + y.limbs[1] + c0) & 0xffffffffffffff;
+        const t10 = t1;
+        const c1 = carry1;
+        const carry2 = (x.limbs[2] + y.limbs[2] + c1) >> 56;
+        const t2 = (x.limbs[2] + y.limbs[2] + c1) & 0xffffffffffffff;
+        const t20 = t2;
+        const c2 = carry2;
+        const carry = (x.limbs[3] + y.limbs[3] + c2) >> 56;
+        const t3 = (x.limbs[3] + y.limbs[3] + c2) & 0xffffffffffffff;
+        const t30 = t3;
+        const c3 = carry;
+        const t4 = x.limbs[4] + y.limbs[4] + c3;
+
+        const y01: u64 = 5175514460705773;
+        const y11: u64 = 70332060721272408;
+        const y21: u64 = 5342;
+        const y31: u64 = 0;
+        const y41: u64 = 268435456;
+
+        const b5 = (t00 -% y01) >> 63;
+        const t5 = ((b5 << 56) + t00) -% y01;
+        const b0 = b5;
+        const t01 = t5;
+        const b6 = (t10 -% (y11 + b0)) >> 63;
+        const t6 = ((b6 << 56) + t10) -% (y11 + b0);
+        const b1 = b6;
+        const t11 = t6;
+        const b7 = (t20 -% (y21 + b1)) >> 63;
+        const t7 = ((b7 << 56) + t20) -% (y21 + b1);
+        const b2 = b7;
+        const t21 = t7;
+        const b8 = (t30 -% (y31 + b2)) >> 63;
+        const t8 = ((b8 << 56) + t30) -% (y31 + b2);
+        const b3 = b8;
+        const t31 = t8;
+        const b = (t4 -% (y41 + b3)) >> 63;
+        const t = ((b << 56) + t4) -% (y41 + b3);
+        const b4 = b;
+        const t41 = t;
+
+        const mask = (b4 -% 1);
+        const z00 = t00 ^ (mask & (t00 ^ t01));
+        const z10 = t10 ^ (mask & (t10 ^ t11));
+        const z20 = t20 ^ (mask & (t20 ^ t21));
+        const z30 = t30 ^ (mask & (t30 ^ t31));
+        const z40 = t4 ^ (mask & (t4 ^ t41));
+
+        return Scalar{ .limbs = .{ z00, z10, z20, z30, z40 } };
+    }
+
+    /// Return x*r (mod l)
+    pub fn mul(x: Scalar, y: Scalar) Scalar {
+        const xy000 = @as(u128, x.limbs[0]) * @as(u128, y.limbs[0]);
+        const xy010 = @as(u128, x.limbs[0]) * @as(u128, y.limbs[1]);
+        const xy020 = @as(u128, x.limbs[0]) * @as(u128, y.limbs[2]);
+        const xy030 = @as(u128, x.limbs[0]) * @as(u128, y.limbs[3]);
+        const xy040 = @as(u128, x.limbs[0]) * @as(u128, y.limbs[4]);
+        const xy100 = @as(u128, x.limbs[1]) * @as(u128, y.limbs[0]);
+        const xy110 = @as(u128, x.limbs[1]) * @as(u128, y.limbs[1]);
+        const xy120 = @as(u128, x.limbs[1]) * @as(u128, y.limbs[2]);
+        const xy130 = @as(u128, x.limbs[1]) * @as(u128, y.limbs[3]);
+        const xy140 = @as(u128, x.limbs[1]) * @as(u128, y.limbs[4]);
+        const xy200 = @as(u128, x.limbs[2]) * @as(u128, y.limbs[0]);
+        const xy210 = @as(u128, x.limbs[2]) * @as(u128, y.limbs[1]);
+        const xy220 = @as(u128, x.limbs[2]) * @as(u128, y.limbs[2]);
+        const xy230 = @as(u128, x.limbs[2]) * @as(u128, y.limbs[3]);
+        const xy240 = @as(u128, x.limbs[2]) * @as(u128, y.limbs[4]);
+        const xy300 = @as(u128, x.limbs[3]) * @as(u128, y.limbs[0]);
+        const xy310 = @as(u128, x.limbs[3]) * @as(u128, y.limbs[1]);
+        const xy320 = @as(u128, x.limbs[3]) * @as(u128, y.limbs[2]);
+        const xy330 = @as(u128, x.limbs[3]) * @as(u128, y.limbs[3]);
+        const xy340 = @as(u128, x.limbs[3]) * @as(u128, y.limbs[4]);
+        const xy400 = @as(u128, x.limbs[4]) * @as(u128, y.limbs[0]);
+        const xy410 = @as(u128, x.limbs[4]) * @as(u128, y.limbs[1]);
+        const xy420 = @as(u128, x.limbs[4]) * @as(u128, y.limbs[2]);
+        const xy430 = @as(u128, x.limbs[4]) * @as(u128, y.limbs[3]);
+        const xy440 = @as(u128, x.limbs[4]) * @as(u128, y.limbs[4]);
+        const z00 = xy000;
+        const z10 = xy010 + xy100;
+        const z20 = xy020 + xy110 + xy200;
+        const z30 = xy030 + xy120 + xy210 + xy300;
+        const z40 = xy040 + xy130 + xy220 + xy310 + xy400;
+        const z50 = xy140 + xy230 + xy320 + xy410;
+        const z60 = xy240 + xy330 + xy420;
+        const z70 = xy340 + xy430;
+        const z80 = xy440;
+
+        const carry0 = z00 >> 56;
+        const t10 = @truncate(u64, z00) & 0xffffffffffffff;
+        const c00 = carry0;
+        const t00 = t10;
+        const carry1 = (z10 + c00) >> 56;
+        const t11 = @truncate(u64, (z10 + c00)) & 0xffffffffffffff;
+        const c10 = carry1;
+        const t12 = t11;
+        const carry2 = (z20 + c10) >> 56;
+        const t13 = @truncate(u64, (z20 + c10)) & 0xffffffffffffff;
+        const c20 = carry2;
+        const t20 = t13;
+        const carry3 = (z30 + c20) >> 56;
+        const t14 = @truncate(u64, (z30 + c20)) & 0xffffffffffffff;
+        const c30 = carry3;
+        const t30 = t14;
+        const carry4 = (z40 + c30) >> 56;
+        const t15 = @truncate(u64, (z40 + c30)) & 0xffffffffffffff;
+        const c40 = carry4;
+        const t40 = t15;
+        const carry5 = (z50 + c40) >> 56;
+        const t16 = @truncate(u64, (z50 + c40)) & 0xffffffffffffff;
+        const c50 = carry5;
+        const t50 = t16;
+        const carry6 = (z60 + c50) >> 56;
+        const t17 = @truncate(u64, (z60 + c50)) & 0xffffffffffffff;
+        const c60 = carry6;
+        const t60 = t17;
+        const carry7 = (z70 + c60) >> 56;
+        const t18 = @truncate(u64, (z70 + c60)) & 0xffffffffffffff;
+        const c70 = carry7;
+        const t70 = t18;
+        const carry8 = (z80 + c70) >> 56;
+        const t19 = @truncate(u64, (z80 + c70)) & 0xffffffffffffff;
+        const c80 = carry8;
+        const t80 = t19;
+        const t90 = (@truncate(u64, c80));
+        const r0 = t00;
+        const r1 = t12;
+        const r2 = t20;
+        const r3 = t30;
+        const r4 = t40;
+        const r5 = t50;
+        const r6 = t60;
+        const r7 = t70;
+        const r8 = t80;
+        const r9 = t90;
+
+        const m0: u64 = 5175514460705773;
+        const m1: u64 = 70332060721272408;
+        const m2: u64 = 5342;
+        const m3: u64 = 0;
+        const m4: u64 = 268435456;
+        const mu0: u64 = 44162584779952923;
+        const mu1: u64 = 9390964836247533;
+        const mu2: u64 = 72057594036560134;
+        const mu3: u64 = 72057594037927935;
+        const mu4: u64 = 68719476735;
+
+        const y_ = (r5 & 0xffffff) << 32;
+        const x_ = r4 >> 24;
+        const z01 = (x_ | y_);
+        const y_0 = (r6 & 0xffffff) << 32;
+        const x_0 = r5 >> 24;
+        const z11 = (x_0 | y_0);
+        const y_1 = (r7 & 0xffffff) << 32;
+        const x_1 = r6 >> 24;
+        const z21 = (x_1 | y_1);
+        const y_2 = (r8 & 0xffffff) << 32;
+        const x_2 = r7 >> 24;
+        const z31 = (x_2 | y_2);
+        const y_3 = (r9 & 0xffffff) << 32;
+        const x_3 = r8 >> 24;
+        const z41 = (x_3 | y_3);
+        const q0 = z01;
+        const q1 = z11;
+        const q2 = z21;
+        const q3 = z31;
+        const q4 = z41;
+        const xy001 = @as(u128, q0) * @as(u128, mu0);
+        const xy011 = @as(u128, q0) * @as(u128, mu1);
+        const xy021 = @as(u128, q0) * @as(u128, mu2);
+        const xy031 = @as(u128, q0) * @as(u128, mu3);
+        const xy041 = @as(u128, q0) * @as(u128, mu4);
+        const xy101 = @as(u128, q1) * @as(u128, mu0);
+        const xy111 = @as(u128, q1) * @as(u128, mu1);
+        const xy121 = @as(u128, q1) * @as(u128, mu2);
+        const xy131 = @as(u128, q1) * @as(u128, mu3);
+        const xy14 = @as(u128, q1) * @as(u128, mu4);
+        const xy201 = @as(u128, q2) * @as(u128, mu0);
+        const xy211 = @as(u128, q2) * @as(u128, mu1);
+        const xy221 = @as(u128, q2) * @as(u128, mu2);
+        const xy23 = @as(u128, q2) * @as(u128, mu3);
+        const xy24 = @as(u128, q2) * @as(u128, mu4);
+        const xy301 = @as(u128, q3) * @as(u128, mu0);
+        const xy311 = @as(u128, q3) * @as(u128, mu1);
+        const xy32 = @as(u128, q3) * @as(u128, mu2);
+        const xy33 = @as(u128, q3) * @as(u128, mu3);
+        const xy34 = @as(u128, q3) * @as(u128, mu4);
+        const xy401 = @as(u128, q4) * @as(u128, mu0);
+        const xy41 = @as(u128, q4) * @as(u128, mu1);
+        const xy42 = @as(u128, q4) * @as(u128, mu2);
+        const xy43 = @as(u128, q4) * @as(u128, mu3);
+        const xy44 = @as(u128, q4) * @as(u128, mu4);
+        const z02 = xy001;
+        const z12 = xy011 + xy101;
+        const z22 = xy021 + xy111 + xy201;
+        const z32 = xy031 + xy121 + xy211 + xy301;
+        const z42 = xy041 + xy131 + xy221 + xy311 + xy401;
+        const z5 = xy14 + xy23 + xy32 + xy41;
+        const z6 = xy24 + xy33 + xy42;
+        const z7 = xy34 + xy43;
+        const z8 = xy44;
+
+        const carry9 = z02 >> 56;
+        const c01 = carry9;
+        const carry10 = (z12 + c01) >> 56;
+        const t21 = @truncate(u64, z12 + c01) & 0xffffffffffffff;
+        const c11 = carry10;
+        const carry11 = (z22 + c11) >> 56;
+        const t22 = @truncate(u64, z22 + c11) & 0xffffffffffffff;
+        const c21 = carry11;
+        const carry12 = (z32 + c21) >> 56;
+        const t23 = @truncate(u64, z32 + c21) & 0xffffffffffffff;
+        const c31 = carry12;
+        const carry13 = (z42 + c31) >> 56;
+        const t24 = @truncate(u64, z42 + c31) & 0xffffffffffffff;
+        const c41 = carry13;
+        const t41 = t24;
+        const carry14 = (z5 + c41) >> 56;
+        const t25 = @truncate(u64, z5 + c41) & 0xffffffffffffff;
+        const c5 = carry14;
+        const t5 = t25;
+        const carry15 = (z6 + c5) >> 56;
+        const t26 = @truncate(u64, z6 + c5) & 0xffffffffffffff;
+        const c6 = carry15;
+        const t6 = t26;
+        const carry16 = (z7 + c6) >> 56;
+        const t27 = @truncate(u64, z7 + c6) & 0xffffffffffffff;
+        const c7 = carry16;
+        const t7 = t27;
+        const carry17 = (z8 + c7) >> 56;
+        const t28 = @truncate(u64, z8 + c7) & 0xffffffffffffff;
+        const c8 = carry17;
+        const t8 = t28;
+        const t9 = @truncate(u64, c8);
+
+        const qmu4_ = t41;
+        const qmu5_ = t5;
+        const qmu6_ = t6;
+        const qmu7_ = t7;
+        const qmu8_ = t8;
+        const qmu9_ = t9;
+        const y_4 = (qmu5_ & 0xffffffffff) << 16;
+        const x_4 = qmu4_ >> 40;
+        const z03 = (x_4 | y_4);
+        const y_5 = (qmu6_ & 0xffffffffff) << 16;
+        const x_5 = qmu5_ >> 40;
+        const z13 = (x_5 | y_5);
+        const y_6 = (qmu7_ & 0xffffffffff) << 16;
+        const x_6 = qmu6_ >> 40;
+        const z23 = (x_6 | y_6);
+        const y_7 = (qmu8_ & 0xffffffffff) << 16;
+        const x_7 = qmu7_ >> 40;
+        const z33 = (x_7 | y_7);
+        const y_8 = (qmu9_ & 0xffffffffff) << 16;
+        const x_8 = qmu8_ >> 40;
+        const z43 = (x_8 | y_8);
+        const qdiv0 = z03;
+        const qdiv1 = z13;
+        const qdiv2 = z23;
+        const qdiv3 = z33;
+        const qdiv4 = z43;
+        const r01 = r0;
+        const r11 = r1;
+        const r21 = r2;
+        const r31 = r3;
+        const r41 = (r4 & 0xffffffffff);
+
+        const xy00 = @as(u128, qdiv0) * @as(u128, m0);
+        const xy01 = @as(u128, qdiv0) * @as(u128, m1);
+        const xy02 = @as(u128, qdiv0) * @as(u128, m2);
+        const xy03 = @as(u128, qdiv0) * @as(u128, m3);
+        const xy04 = @as(u128, qdiv0) * @as(u128, m4);
+        const xy10 = @as(u128, qdiv1) * @as(u128, m0);
+        const xy11 = @as(u128, qdiv1) * @as(u128, m1);
+        const xy12 = @as(u128, qdiv1) * @as(u128, m2);
+        const xy13 = @as(u128, qdiv1) * @as(u128, m3);
+        const xy20 = @as(u128, qdiv2) * @as(u128, m0);
+        const xy21 = @as(u128, qdiv2) * @as(u128, m1);
+        const xy22 = @as(u128, qdiv2) * @as(u128, m2);
+        const xy30 = @as(u128, qdiv3) * @as(u128, m0);
+        const xy31 = @as(u128, qdiv3) * @as(u128, m1);
+        const xy40 = @as(u128, qdiv4) * @as(u128, m0);
+        const carry18 = xy00 >> 56;
+        const t29 = @truncate(u64, xy00) & 0xffffffffffffff;
+        const c0 = carry18;
+        const t01 = t29;
+        const carry19 = (xy01 + xy10 + c0) >> 56;
+        const t31 = @truncate(u64, xy01 + xy10 + c0) & 0xffffffffffffff;
+        const c12 = carry19;
+        const t110 = t31;
+        const carry20 = (xy02 + xy11 + xy20 + c12) >> 56;
+        const t32 = @truncate(u64, xy02 + xy11 + xy20 + c12) & 0xffffffffffffff;
+        const c22 = carry20;
+        const t210 = t32;
+        const carry = (xy03 + xy12 + xy21 + xy30 + c22) >> 56;
+        const t33 = @truncate(u64, xy03 + xy12 + xy21 + xy30 + c22) & 0xffffffffffffff;
+        const c32 = carry;
+        const t34 = t33;
+        const t42 = @truncate(u64, xy04 + xy13 + xy22 + xy31 + xy40 + c32) & 0xffffffffff;
+
+        const qmul0 = t01;
+        const qmul1 = t110;
+        const qmul2 = t210;
+        const qmul3 = t34;
+        const qmul4 = t42;
+        const b5 = (r01 -% qmul0) >> 63;
+        const t35 = ((b5 << 56) + r01) -% qmul0;
+        const c1 = b5;
+        const t02 = t35;
+        const b6 = (r11 -% (qmul1 + c1)) >> 63;
+        const t36 = ((b6 << 56) + r11) -% (qmul1 + c1);
+        const c2 = b6;
+        const t111 = t36;
+        const b7 = (r21 -% (qmul2 + c2)) >> 63;
+        const t37 = ((b7 << 56) + r21) -% (qmul2 + c2);
+        const c3 = b7;
+        const t211 = t37;
+        const b8 = (r31 -% (qmul3 + c3)) >> 63;
+        const t38 = ((b8 << 56) + r31) -% (qmul3 + c3);
+        const c4 = b8;
+        const t39 = t38;
+        const b9 = (r41 -% (qmul4 + c4)) >> 63;
+        const t43 = ((b9 << 40) + r41) -% (qmul4 + c4);
+        const t44 = t43;
+        const s0 = t02;
+        const s1 = t111;
+        const s2 = t211;
+        const s3 = t39;
+        const s4 = t44;
+
+        const y01: u64 = 5175514460705773;
+        const y11: u64 = 70332060721272408;
+        const y21: u64 = 5342;
+        const y31: u64 = 0;
+        const y41: u64 = 268435456;
+
+        const b10 = (s0 -% y01) >> 63;
+        const t45 = ((b10 << 56) + s0) -% y01;
+        const b0 = b10;
+        const t0 = t45;
+        const b11 = (s1 -% (y11 + b0)) >> 63;
+        const t46 = ((b11 << 56) + s1) -% (y11 + b0);
+        const b1 = b11;
+        const t1 = t46;
+        const b12 = (s2 -% (y21 + b1)) >> 63;
+        const t47 = ((b12 << 56) + s2) -% (y21 + b1);
+        const b2 = b12;
+        const t2 = t47;
+        const b13 = (s3 -% (y31 + b2)) >> 63;
+        const t48 = ((b13 << 56) + s3) -% (y31 + b2);
+        const b3 = b13;
+        const t3 = t48;
+        const b = (s4 -% (y41 + b3)) >> 63;
+        const t = ((b << 56) + s4) -% (y41 + b3);
+        const b4 = b;
+        const t4 = t;
+        const mask = (b4 -% @intCast(u64, ((1))));
+        const z04 = s0 ^ (mask & (s0 ^ t0));
+        const z14 = s1 ^ (mask & (s1 ^ t1));
+        const z24 = s2 ^ (mask & (s2 ^ t2));
+        const z34 = s3 ^ (mask & (s3 ^ t3));
+        const z44 = s4 ^ (mask & (s4 ^ t4));
+
+        return Scalar{ .limbs = .{ z04, z14, z24, z34, z44 } };
+    }
+};
+
+const ScalarDouble = struct {
+    const Limbs = [10]u64;
+    limbs: Limbs = undefined,
+
+    fn fromBytes64(bytes: [64]u8) ScalarDouble {
+        var limbs: Limbs = undefined;
+        var i: usize = 0;
+        while (i < 9) : (i += 1) {
+            limbs[i] = mem.readIntLittle(u64, bytes[i * 7 ..][0..8]) & 0xffffffffffffff;
+        }
+        limbs[i] = @as(u64, bytes[i * 7]);
+        return ScalarDouble{ .limbs = limbs };
+    }
+
+    fn fromBytes32(bytes: [32]u8) ScalarDouble {
+        var limbs: Limbs = undefined;
+        var i: usize = 0;
+        while (i < 4) : (i += 1) {
+            limbs[i] = mem.readIntLittle(u64, bytes[i * 7 ..][0..8]) & 0xffffffffffffff;
+        }
+        limbs[i] = @as(u64, mem.readIntLittle(u32, bytes[i * 7 ..][0..4]));
+        mem.set(u64, limbs[5..], 0);
+        return ScalarDouble{ .limbs = limbs };
+    }
+
+    fn toBytes(expanded_double: *ScalarDouble) [32]u8 {
+        return expanded_double.reduce(10).toBytes();
+    }
+
+    /// Barrett reduction
+    fn reduce(expanded: *ScalarDouble, comptime limbs_count: usize) Scalar {
+        const t = expanded.limbs;
+        const t0 = if (limbs_count <= 0) 0 else t[0];
+        const t1 = if (limbs_count <= 1) 0 else t[1];
+        const t2 = if (limbs_count <= 2) 0 else t[2];
+        const t3 = if (limbs_count <= 3) 0 else t[3];
+        const t4 = if (limbs_count <= 4) 0 else t[4];
+        const t5 = if (limbs_count <= 5) 0 else t[5];
+        const t6 = if (limbs_count <= 6) 0 else t[6];
+        const t7 = if (limbs_count <= 7) 0 else t[7];
+        const t8 = if (limbs_count <= 8) 0 else t[8];
+        const t9 = if (limbs_count <= 9) 0 else t[9];
+
+        const m0: u64 = 5175514460705773;
+        const m1: u64 = 70332060721272408;
+        const m2: u64 = 5342;
+        const m3: u64 = 0;
+        const m4: u64 = 268435456;
+        const mu0: u64 = 44162584779952923;
+        const mu1: u64 = 9390964836247533;
+        const mu2: u64 = 72057594036560134;
+        const mu3: u64 = 0xffffffffffffff;
+        const mu4: u64 = 68719476735;
+
+        const y_ = (t5 & 0xffffff) << 32;
+        const x_ = t4 >> 24;
+        const z00 = x_ | y_;
+        const y_0 = (t6 & 0xffffff) << 32;
+        const x_0 = t5 >> 24;
+        const z10 = x_0 | y_0;
+        const y_1 = (t7 & 0xffffff) << 32;
+        const x_1 = t6 >> 24;
+        const z20 = x_1 | y_1;
+        const y_2 = (t8 & 0xffffff) << 32;
+        const x_2 = t7 >> 24;
+        const z30 = x_2 | y_2;
+        const y_3 = (t9 & 0xffffff) << 32;
+        const x_3 = t8 >> 24;
+        const z40 = x_3 | y_3;
+        const q0 = z00;
+        const q1 = z10;
+        const q2 = z20;
+        const q3 = z30;
+        const q4 = z40;
+
+        const xy000 = @as(u128, q0) * @as(u128, mu0);
+        const xy010 = @as(u128, q0) * @as(u128, mu1);
+        const xy020 = @as(u128, q0) * @as(u128, mu2);
+        const xy030 = @as(u128, q0) * @as(u128, mu3);
+        const xy040 = @as(u128, q0) * @as(u128, mu4);
+        const xy100 = @as(u128, q1) * @as(u128, mu0);
+        const xy110 = @as(u128, q1) * @as(u128, mu1);
+        const xy120 = @as(u128, q1) * @as(u128, mu2);
+        const xy130 = @as(u128, q1) * @as(u128, mu3);
+        const xy14 = @as(u128, q1) * @as(u128, mu4);
+        const xy200 = @as(u128, q2) * @as(u128, mu0);
+        const xy210 = @as(u128, q2) * @as(u128, mu1);
+        const xy220 = @as(u128, q2) * @as(u128, mu2);
+        const xy23 = @as(u128, q2) * @as(u128, mu3);
+        const xy24 = @as(u128, q2) * @as(u128, mu4);
+        const xy300 = @as(u128, q3) * @as(u128, mu0);
+        const xy310 = @as(u128, q3) * @as(u128, mu1);
+        const xy32 = @as(u128, q3) * @as(u128, mu2);
+        const xy33 = @as(u128, q3) * @as(u128, mu3);
+        const xy34 = @as(u128, q3) * @as(u128, mu4);
+        const xy400 = @as(u128, q4) * @as(u128, mu0);
+        const xy41 = @as(u128, q4) * @as(u128, mu1);
+        const xy42 = @as(u128, q4) * @as(u128, mu2);
+        const xy43 = @as(u128, q4) * @as(u128, mu3);
+        const xy44 = @as(u128, q4) * @as(u128, mu4);
+        const z01 = xy000;
+        const z11 = xy010 + xy100;
+        const z21 = xy020 + xy110 + xy200;
+        const z31 = xy030 + xy120 + xy210 + xy300;
+        const z41 = xy040 + xy130 + xy220 + xy310 + xy400;
+        const z5 = xy14 + xy23 + xy32 + xy41;
+        const z6 = xy24 + xy33 + xy42;
+        const z7 = xy34 + xy43;
+        const z8 = xy44;
+
+        const carry0 = z01 >> 56;
+        const c00 = carry0;
+        const carry1 = (z11 + c00) >> 56;
+        const t100 = @as(u64, @truncate(u64, z11 + c00)) & 0xffffffffffffff;
+        const c10 = carry1;
+        const carry2 = (z21 + c10) >> 56;
+        const t101 = @as(u64, @truncate(u64, z21 + c10)) & 0xffffffffffffff;
+        const c20 = carry2;
+        const carry3 = (z31 + c20) >> 56;
+        const t102 = @as(u64, @truncate(u64, z31 + c20)) & 0xffffffffffffff;
+        const c30 = carry3;
+        const carry4 = (z41 + c30) >> 56;
+        const t103 = @as(u64, @truncate(u64, z41 + c30)) & 0xffffffffffffff;
+        const c40 = carry4;
+        const t410 = t103;
+        const carry5 = (z5 + c40) >> 56;
+        const t104 = @as(u64, @truncate(u64, z5 + c40)) & 0xffffffffffffff;
+        const c5 = carry5;
+        const t51 = t104;
+        const carry6 = (z6 + c5) >> 56;
+        const t105 = @as(u64, @truncate(u64, z6 + c5)) & 0xffffffffffffff;
+        const c6 = carry6;
+        const t61 = t105;
+        const carry7 = (z7 + c6) >> 56;
+        const t106 = @as(u64, @truncate(u64, z7 + c6)) & 0xffffffffffffff;
+        const c7 = carry7;
+        const t71 = t106;
+        const carry8 = (z8 + c7) >> 56;
+        const t107 = @as(u64, @truncate(u64, z8 + c7)) & 0xffffffffffffff;
+        const c8 = carry8;
+        const t81 = t107;
+        const t91 = @as(u64, @truncate(u64, c8));
+
+        const qmu4_ = t410;
+        const qmu5_ = t51;
+        const qmu6_ = t61;
+        const qmu7_ = t71;
+        const qmu8_ = t81;
+        const qmu9_ = t91;
+        const y_4 = (qmu5_ & 0xffffffffff) << 16;
+        const x_4 = qmu4_ >> 40;
+        const z02 = x_4 | y_4;
+        const y_5 = (qmu6_ & 0xffffffffff) << 16;
+        const x_5 = qmu5_ >> 40;
+        const z12 = x_5 | y_5;
+        const y_6 = (qmu7_ & 0xffffffffff) << 16;
+        const x_6 = qmu6_ >> 40;
+        const z22 = x_6 | y_6;
+        const y_7 = (qmu8_ & 0xffffffffff) << 16;
+        const x_7 = qmu7_ >> 40;
+        const z32 = x_7 | y_7;
+        const y_8 = (qmu9_ & 0xffffffffff) << 16;
+        const x_8 = qmu8_ >> 40;
+        const z42 = x_8 | y_8;
+        const qdiv0 = z02;
+        const qdiv1 = z12;
+        const qdiv2 = z22;
+        const qdiv3 = z32;
+        const qdiv4 = z42;
+        const r0 = t0;
+        const r1 = t1;
+        const r2 = t2;
+        const r3 = t3;
+        const r4 = t4 & 0xffffffffff;
+
+        const xy00 = @as(u128, qdiv0) * @as(u128, m0);
+        const xy01 = @as(u128, qdiv0) * @as(u128, m1);
+        const xy02 = @as(u128, qdiv0) * @as(u128, m2);
+        const xy03 = @as(u128, qdiv0) * @as(u128, m3);
+        const xy04 = @as(u128, qdiv0) * @as(u128, m4);
+        const xy10 = @as(u128, qdiv1) * @as(u128, m0);
+        const xy11 = @as(u128, qdiv1) * @as(u128, m1);
+        const xy12 = @as(u128, qdiv1) * @as(u128, m2);
+        const xy13 = @as(u128, qdiv1) * @as(u128, m3);
+        const xy20 = @as(u128, qdiv2) * @as(u128, m0);
+        const xy21 = @as(u128, qdiv2) * @as(u128, m1);
+        const xy22 = @as(u128, qdiv2) * @as(u128, m2);
+        const xy30 = @as(u128, qdiv3) * @as(u128, m0);
+        const xy31 = @as(u128, qdiv3) * @as(u128, m1);
+        const xy40 = @as(u128, qdiv4) * @as(u128, m0);
+        const carry9 = xy00 >> 56;
+        const t108 = @truncate(u64, xy00) & 0xffffffffffffff;
+        const c0 = carry9;
+        const t010 = t108;
+        const carry10 = (xy01 + xy10 + c0) >> 56;
+        const t109 = @truncate(u64, xy01 + xy10 + c0) & 0xffffffffffffff;
+        const c11 = carry10;
+        const t110 = t109;
+        const carry11 = (xy02 + xy11 + xy20 + c11) >> 56;
+        const t1010 = @truncate(u64, xy02 + xy11 + xy20 + c11) & 0xffffffffffffff;
+        const c21 = carry11;
+        const t210 = t1010;
+        const carry = (xy03 + xy12 + xy21 + xy30 + c21) >> 56;
+        const t1011 = @truncate(u64, xy03 + xy12 + xy21 + xy30 + c21) & 0xffffffffffffff;
+        const c31 = carry;
+        const t310 = t1011;
+        const t411 = @truncate(u64, xy04 + xy13 + xy22 + xy31 + xy40 + c31) & 0xffffffffff;
+
+        const qmul0 = t010;
+        const qmul1 = t110;
+        const qmul2 = t210;
+        const qmul3 = t310;
+        const qmul4 = t411;
+        const b5 = (r0 -% qmul0) >> 63;
+        const t1012 = ((b5 << 56) + r0) -% qmul0;
+        const c1 = b5;
+        const t011 = t1012;
+        const b6 = (r1 -% (qmul1 + c1)) >> 63;
+        const t1013 = ((b6 << 56) + r1) -% (qmul1 + c1);
+        const c2 = b6;
+        const t111 = t1013;
+        const b7 = (r2 -% (qmul2 + c2)) >> 63;
+        const t1014 = ((b7 << 56) + r2) -% (qmul2 + c2);
+        const c3 = b7;
+        const t211 = t1014;
+        const b8 = (r3 -% (qmul3 + c3)) >> 63;
+        const t1015 = ((b8 << 56) + r3) -% (qmul3 + c3);
+        const c4 = b8;
+        const t311 = t1015;
+        const b9 = (r4 -% (qmul4 + c4)) >> 63;
+        const t1016 = ((b9 << 40) + r4) -% (qmul4 + c4);
+        const t412 = t1016;
+        const s0 = t011;
+        const s1 = t111;
+        const s2 = t211;
+        const s3 = t311;
+        const s4 = t412;
+
+        const y0: u64 = 5175514460705773;
+        const y1: u64 = 70332060721272408;
+        const y2: u64 = 5342;
+        const y3: u64 = 0;
+        const y4: u64 = 268435456;
+
+        const b10 = (s0 -% y0) >> 63;
+        const t1017 = ((b10 << 56) + s0) -% y0;
+        const b0 = b10;
+        const t01 = t1017;
+        const b11 = (s1 -% (y1 + b0)) >> 63;
+        const t1018 = ((b11 << 56) + s1) -% (y1 + b0);
+        const b1 = b11;
+        const t11 = t1018;
+        const b12 = (s2 -% (y2 + b1)) >> 63;
+        const t1019 = ((b12 << 56) + s2) -% (y2 + b1);
+        const b2 = b12;
+        const t21 = t1019;
+        const b13 = (s3 -% (y3 + b2)) >> 63;
+        const t1020 = ((b13 << 56) + s3) -% (y3 + b2);
+        const b3 = b13;
+        const t31 = t1020;
+        const b = (s4 -% (y4 + b3)) >> 63;
+        const t10 = ((b << 56) + s4) -% (y4 + b3);
+        const b4 = b;
+        const t41 = t10;
+        const mask = b4 -% @as(u64, @as(u64, 1));
+        const z03 = s0 ^ (mask & (s0 ^ t01));
+        const z13 = s1 ^ (mask & (s1 ^ t11));
+        const z23 = s2 ^ (mask & (s2 ^ t21));
+        const z33 = s3 ^ (mask & (s3 ^ t31));
+        const z43 = s4 ^ (mask & (s4 ^ t41));
+
+        return Scalar{ .limbs = .{ z03, z13, z23, z33, z43 } };
+    }
+};
+
 test "scalar25519" {
     const bytes: [32]u8 = .{ 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 255 };
-    var x = ScalarExpanded.fromBytes(bytes);
+    var x = Scalar.fromBytes(bytes);
     var y = x.toBytes();
     try rejectNonCanonical(y);
     var buf: [128]u8 = undefined;