diff --git a/x/dhkem-secp256k1/README.md b/x/dhkem-secp256k1/README.md
index 836c1c739..0f37b6459 100644
--- a/x/dhkem-secp256k1/README.md
+++ b/x/dhkem-secp256k1/README.md
@@ -1,7 +1,7 @@
 <h1 align="center">@hpke/dhkem-secp256k1</h1>
 
 <div align="center">
-A TypeScript <a href="https://datatracker.ietf.org/doc/html/rfc9180">Hybrid Public Key Encryption (HPKE)</a> module extension for DH-KEM with secp256k1 curve, which is implemented by using [@noble/curves/secp256k1](https://github.com/paulmillr/noble-curves). Note that the extension is EXPERIMENTAL and NOT STANDARDIZED.</div>
+A TypeScript <a href="https://datatracker.ietf.org/doc/html/rfc9180">Hybrid Public Key Encryption (HPKE)</a> module extension for DH-KEM with secp256k1 curve, which is implemented by using <a href="https://github.com/paulmillr/noble-curves">@noble/curves/secp256k1</a>. Note that the extension is EXPERIMENTAL and NOT STANDARDIZED.</div>
 <p></p>
 
 <div align="center">
diff --git a/x/dhkem-secp256k1/src/dhkem-secp256k1.ts b/x/dhkem-secp256k1/src/dhkem-secp256k1.ts
index b9d565566..6863aa7a2 100644
--- a/x/dhkem-secp256k1/src/dhkem-secp256k1.ts
+++ b/x/dhkem-secp256k1/src/dhkem-secp256k1.ts
@@ -131,11 +131,28 @@ class Secp256k1 extends Algorithm implements KemPrimitives {
   }
 }
 
+/**
+ * The class of the DH-KEM with secp256k1 curve.
+ *
+ * The public keys are assumed to be compressed.
+ * Note that it is experimental and not standardized.
+ *
+ * The instance of this class can be specified to the CipherSuiteParams as follows:
+ *
+ * @example
+ * import { KdfId, AeadId, CipherSuite } from "http://deno.land/x/hpke/mod.ts";
+ * import { DhkemSecp256k1HkdfSha256} from "https://deno.land/x/hpke/x/dhkem-secp256k1/mod.ts";
+ * const suite = new CipherSuite({
+ *   kem: new DhkemSecp256k1HkdfSha256(),
+ *   kdf: KdfId.HkdfSha256,
+ *   aead: AeadId.Aes128Gcm,
+ * });
+ */
 export class DhkemSecp256k1HkdfSha256 extends Dhkem implements KemInterface {
-  public readonly id: KemId = KemId.DhkemSecp256K1HkdfSha256;
+  public readonly id: KemId = KemId.DhkemSecp256k1HkdfSha256;
   public readonly secretSize: number = 32;
-  public readonly encSize: number = 65;
-  public readonly publicKeySize: number = 65;
+  public readonly encSize: number = 33;
+  public readonly publicKeySize: number = 33;
   public readonly privateKeySize: number = 32;
 
   constructor() {
diff --git a/x/dhkem-secp256k1/test/dhkem-secp256k1.test.ts b/x/dhkem-secp256k1/test/dhkem-secp256k1.test.ts
index 583e5a3cd..8f300121b 100644
--- a/x/dhkem-secp256k1/test/dhkem-secp256k1.test.ts
+++ b/x/dhkem-secp256k1/test/dhkem-secp256k1.test.ts
@@ -59,7 +59,7 @@ async function loadSubtleCrypto(): Promise<SubtleCrypto> {
   }
 }
 
-describe("DhkemP256k1Hkdf256", () => {
+describe("DhkemSecp256k1Hkdf256", () => {
   describe("with valid parameters", () => {
     it("should have a correct KEM object", async () => {
       const api = await loadSubtleCrypto();
@@ -70,8 +70,8 @@ describe("DhkemP256k1Hkdf256", () => {
       assertEquals(typeof dhkemSecp256k1, "object");
       assertEquals(dhkemSecp256k1.id, KemId.DhkemSecp256K1HkdfSha256);
       assertEquals(dhkemSecp256k1.secretSize, 32);
-      assertEquals(dhkemSecp256k1.encSize, 65);
-      assertEquals(dhkemSecp256k1.publicKeySize, 65);
+      assertEquals(dhkemSecp256k1.encSize, 33);
+      assertEquals(dhkemSecp256k1.publicKeySize, 33);
       assertEquals(dhkemSecp256k1.privateKeySize, 32);
     });
   });
@@ -230,8 +230,8 @@ describe("CipherSuite", () => {
       });
       const kem = await suite.kemContext();
       assertEquals(kem.secretSize, 32);
-      assertEquals(kem.encSize, 65);
-      assertEquals(kem.publicKeySize, 65);
+      assertEquals(kem.encSize, 33);
+      assertEquals(kem.publicKeySize, 33);
       assertEquals(kem.privateKeySize, 32);
 
       // assert
@@ -247,8 +247,9 @@ describe("CipherSuite", () => {
   describe("A README example of Base mode (DhkemSecp256k1HkdfSha256/KdfId.HkdfSha256)", () => {
     it("should work normally", async () => {
       // setup
+      const kemInstance = new DhkemSecp256k1HkdfSha256();
       const suite = new CipherSuite({
-        kem: new DhkemSecp256k1HkdfSha256(),
+        kem: kemInstance,
         kdf: KdfId.HkdfSha256,
         aead: AeadId.Aes128Gcm,
       });
@@ -263,6 +264,8 @@ describe("CipherSuite", () => {
         recipientKey: rkp,
         enc: sender.enc,
       });
+      assertEquals(sender.enc.byteLength, kemInstance.encSize);
+      assertEquals(sender.enc.byteLength, kemInstance.publicKeySize);
 
       // encrypt
       const ct = await sender.seal(