diff --git a/src/keys/symmetric.ts b/src/keys/symmetric.ts
index b517e46..7dfc742 100644
--- a/src/keys/symmetric.ts
+++ b/src/keys/symmetric.ts
@@ -3,6 +3,6 @@ import { CryptoKey } from "./key";
 export class SymmetricKey extends CryptoKey {
 
   public override readonly kty = "oct";
-  public override readonly type: "secret" = "secret";
+  public override readonly type = "secret" as const;
 
 }
diff --git a/src/mechs/ec/private_key.ts b/src/mechs/ec/private_key.ts
index 1855223..28c1f72 100644
--- a/src/mechs/ec/private_key.ts
+++ b/src/mechs/ec/private_key.ts
@@ -5,7 +5,7 @@ import { AsymmetricKey } from "../../keys";
 import { getOidByNamedCurve } from "./helper";
 
 export class EcPrivateKey extends AsymmetricKey implements IJsonConvertible {
-  public readonly type: "private" = "private";
+  public readonly type = "private" as const;
   public override algorithm!: EcKeyAlgorithm;
 
   public getKey() {
diff --git a/src/mechs/ec/public_key.ts b/src/mechs/ec/public_key.ts
index 8911228..8a16c51 100644
--- a/src/mechs/ec/public_key.ts
+++ b/src/mechs/ec/public_key.ts
@@ -6,7 +6,7 @@ import { getOidByNamedCurve } from "./helper";
 
 export class EcPublicKey extends AsymmetricKey implements IJsonConvertible {
 
-  public readonly type: "public" = "public";
+  public readonly type = "public" as const;
   public override algorithm!: EcKeyAlgorithm;
 
   public getKey() {
@@ -39,7 +39,7 @@ export class EcPublicKey extends AsymmetricKey implements IJsonConvertible {
     keyInfo.publicKeyAlgorithm.parameters = AsnSerializer.serialize(
       new core.asn1.ObjectIdentifier(getOidByNamedCurve(json.crv)),
     );
-    keyInfo.publicKey = AsnSerializer.toASN(key).valueHex;
+    keyInfo.publicKey = (AsnSerializer.toASN(key) as any).valueHex;
 
     this.data = Buffer.from(AsnSerializer.serialize(keyInfo));
 
diff --git a/src/mechs/ed/private_key.ts b/src/mechs/ed/private_key.ts
index df4b1f6..0040446 100644
--- a/src/mechs/ed/private_key.ts
+++ b/src/mechs/ed/private_key.ts
@@ -5,7 +5,7 @@ import { AsymmetricKey } from "../../keys";
 import { getOidByNamedCurve } from "./helper";
 
 export class EdPrivateKey extends AsymmetricKey implements IJsonConvertible {
-  public readonly type: "private" = "private";
+  public readonly type = "private" as const;
   public override algorithm!: EcKeyAlgorithm;
 
   public getKey() {
diff --git a/src/mechs/ed/public_key.ts b/src/mechs/ed/public_key.ts
index 939a013..3262238 100644
--- a/src/mechs/ed/public_key.ts
+++ b/src/mechs/ed/public_key.ts
@@ -7,7 +7,7 @@ import { getOidByNamedCurve } from "./helper";
 
 export class EdPublicKey extends AsymmetricKey implements IJsonConvertible {
 
-  public readonly type: "public" = "public";
+  public readonly type = "public" as const;
   public override algorithm!: EcKeyAlgorithm;
 
   public getKey() {
diff --git a/src/mechs/rsa/private_key.ts b/src/mechs/rsa/private_key.ts
index 0fd17b6..2545147 100644
--- a/src/mechs/rsa/private_key.ts
+++ b/src/mechs/rsa/private_key.ts
@@ -5,7 +5,7 @@ import { AsymmetricKey } from "../../keys";
 import { getJwkAlgorithm } from "./helper";
 
 export class RsaPrivateKey extends AsymmetricKey {
-  public readonly type: "private" = "private";
+  public readonly type = "private" as const;
   public override algorithm!: RsaHashedKeyAlgorithm;
 
   public getKey() {
diff --git a/src/mechs/rsa/public_key.ts b/src/mechs/rsa/public_key.ts
index 32f01d3..ab8c430 100644
--- a/src/mechs/rsa/public_key.ts
+++ b/src/mechs/rsa/public_key.ts
@@ -5,7 +5,7 @@ import { AsymmetricKey } from "../../keys/asymmetric";
 import { getJwkAlgorithm } from "./helper";
 
 export class RsaPublicKey extends AsymmetricKey {
-  public readonly type: "public" = "public";
+  public readonly type = "public" as const;
   public override algorithm!: RsaHashedKeyAlgorithm;
 
   public getKey() {