diff --git a/lib/std/crypto/ecdsa.zig b/lib/std/crypto/ecdsa.zig
index 3360d7bb87..ee27e23a75 100644
--- a/lib/std/crypto/ecdsa.zig
+++ b/lib/std/crypto/ecdsa.zig
@@ -92,10 +92,11 @@ pub fn Ecdsa(comptime Curve: type, comptime Hash: type) type {
                 const s = try Curve.scalar.Scalar.fromBytes(self.s, .Big);
                 if (r.isZero() or s.isZero()) return error.IdentityElement;
 
-                var h: [Hash.digest_length]u8 = undefined;
-                Hash.hash(msg, &h, .{});
-
                 const ht = Curve.scalar.encoded_length;
+                const h_len = @max(Hash.digest_length, ht);
+                var h: [h_len]u8 = [_]u8{0} ** h_len;
+                Hash.hash(msg, h[h_len - Hash.digest_length .. h_len], .{});
+
                 const z = reduceToScalar(ht, h[0..ht].*);
                 if (z.isZero()) {
                     return error.SignatureVerificationFailed;
@@ -228,14 +229,16 @@ pub fn Ecdsa(comptime Curve: type, comptime Hash: type) type {
             pub fn sign(key_pair: KeyPair, msg: []const u8, noise: ?[noise_length]u8) (IdentityElementError || NonCanonicalError)!Signature {
                 const secret_key = key_pair.secret_key;
 
-                var h: [Hash.digest_length]u8 = undefined;
-                Hash.hash(msg, &h, .{});
-
                 const scalar_encoded_length = Curve.scalar.encoded_length;
+                const h_len = @max(Hash.digest_length, scalar_encoded_length);
+                var h: [h_len]u8 = [_]u8{0} ** h_len;
+                var h_slice = h[h_len - Hash.digest_length .. h_len];
+                Hash.hash(msg, h_slice, .{});
+
                 std.debug.assert(h.len >= scalar_encoded_length);
                 const z = reduceToScalar(scalar_encoded_length, h[0..scalar_encoded_length].*);
 
-                const k = deterministicScalar(h, secret_key.bytes, noise);
+                const k = deterministicScalar(h_slice.*, secret_key.bytes, noise);
 
                 const p = try Curve.basePoint.mul(k.toBytes(.Big), .Big);
                 const xs = p.affineCoordinates().x.toBytes(.Big);
@@ -268,6 +271,7 @@ pub fn Ecdsa(comptime Curve: type, comptime Hash: type) type {
         fn deterministicScalar(h: [Hash.digest_length]u8, secret_key: Curve.scalar.CompressedScalar, noise: ?[noise_length]u8) Curve.scalar.Scalar {
             var k = [_]u8{0x00} ** h.len;
             var m = [_]u8{0x00} ** (h.len + 1 + noise_length + secret_key.len + h.len);
+            var t = [_]u8{0x00} ** Curve.scalar.encoded_length;
             const m_v = m[0..h.len];
             const m_i = &m[m_v.len];
             const m_z = m[m_v.len + 1 ..][0..noise_length];
@@ -286,8 +290,13 @@ pub fn Ecdsa(comptime Curve: type, comptime Hash: type) type {
             Hmac.create(&k, &m, &k);
             Hmac.create(m_v, m_v, &k);
             while (true) {
-                Hmac.create(m_v, m_v, &k);
-                if (Curve.scalar.Scalar.fromBytes(m_v[0..Curve.scalar.encoded_length].*, .Big)) |s| return s else |_| {}
+                var t_off: usize = 0;
+                while (t_off < t.len) : (t_off += m_v.len) {
+                    const t_end = @min(t_off + m_v.len, t.len);
+                    Hmac.create(m_v, m_v, &k);
+                    std.mem.copy(u8, t[t_off..t_end], m_v[0 .. t_end - t_off]);
+                }
+                if (Curve.scalar.Scalar.fromBytes(t, .Big)) |s| return s else |_| {}
                 mem.copy(u8, m_v, m_v);
                 m_i.* = 0x00;
                 Hmac.create(&k, m[0 .. m_v.len + 1], &k);
@@ -325,6 +334,55 @@ test "ECDSA - Basic operations over Secp256k1" {
     try sig2.verify(msg, kp.public_key);
 }
 
+test "ECDSA - Basic operations over EcdsaP384Sha256" {
+    const Scheme = Ecdsa(crypto.ecc.P384, crypto.hash.sha2.Sha256);
+    const kp = try Scheme.KeyPair.create(null);
+    const msg = "test";
+
+    var noise: [Scheme.noise_length]u8 = undefined;
+    crypto.random.bytes(&noise);
+    const sig = try kp.sign(msg, noise);
+    try sig.verify(msg, kp.public_key);
+
+    const sig2 = try kp.sign(msg, null);
+    try sig2.verify(msg, kp.public_key);
+}
+
+test "ECDSA - Verifying a existing signature with EcdsaP384Sha256" {
+    const Scheme = Ecdsa(crypto.ecc.P384, crypto.hash.sha2.Sha256);
+    // zig fmt: off
+    const sk_bytes = [_]u8{
+    0x6a, 0x53, 0x9c, 0x83, 0x0f, 0x06, 0x86, 0xd9, 0xef, 0xf1, 0xe7, 0x5c, 0xae,
+    0x93, 0xd9, 0x5b, 0x16, 0x1e, 0x96, 0x7c, 0xb0, 0x86, 0x35, 0xc9, 0xea, 0x20,
+    0xdc, 0x2b, 0x02, 0x37, 0x6d, 0xd2, 0x89, 0x72, 0x0a, 0x37, 0xf6, 0x5d, 0x4f,
+    0x4d, 0xf7, 0x97, 0xcb, 0x8b, 0x03, 0x63, 0xc3, 0x2d
+    };
+    const msg = [_]u8{
+    0x64, 0x61, 0x74, 0x61, 0x20, 0x66, 0x6f, 0x72, 0x20, 0x73, 0x69, 0x67, 0x6e,
+    0x69, 0x6e, 0x67, 0x0a
+    };
+    const sig_ans_bytes = [_]u8{
+    0x30, 0x64, 0x02, 0x30, 0x7a, 0x31, 0xd8, 0xe0, 0xf8, 0x40, 0x7d, 0x6a, 0xf3,
+    0x1a, 0x5d, 0x02, 0xe5, 0xcb, 0x24, 0x29, 0x1a, 0xac, 0x15, 0x94, 0xd1, 0x5b,
+    0xcd, 0x75, 0x2f, 0x45, 0x79, 0x98, 0xf7, 0x60, 0x9a, 0xd5, 0xca, 0x80, 0x15,
+    0x87, 0x9b, 0x0c, 0x27, 0xe3, 0x01, 0x8b, 0x73, 0x4e, 0x57, 0xa3, 0xd2, 0x9a,
+    0x02, 0x30, 0x33, 0xe0, 0x04, 0x5e, 0x76, 0x1f, 0xc8, 0xcf, 0xda, 0xbe, 0x64,
+    0x95, 0x0a, 0xd4, 0x85, 0x34, 0x33, 0x08, 0x7a, 0x81, 0xf2, 0xf6, 0xb6, 0x94,
+    0x68, 0xc3, 0x8c, 0x5f, 0x88, 0x92, 0x27, 0x5e, 0x4e, 0x84, 0x96, 0x48, 0x42,
+    0x84, 0x28, 0xac, 0x37, 0x93, 0x07, 0xd3, 0x50, 0x32, 0x71, 0xb0
+    };
+    // zig fmt: on
+
+    const sk = try Scheme.SecretKey.fromBytes(sk_bytes);
+    const kp = try Scheme.KeyPair.fromSecretKey(sk);
+
+    const sig_ans = try Scheme.Signature.fromDer(&sig_ans_bytes);
+    try sig_ans.verify(&msg, kp.public_key);
+
+    const sig = try kp.sign(&msg, null);
+    try sig.verify(&msg, kp.public_key);
+}
+
 const TestVector = struct {
     key: []const u8,
     msg: []const u8,