diff --git a/source/JSONWebToken-Core.package/JWAHMACSHA256.class/class/checkSignature.withKey..st b/source/JSONWebToken-Core.package/JWAHMACSHA256.class/class/checkSignature.withKey..st
new file mode 100644
index 0000000..c5f1dbe
--- /dev/null
+++ b/source/JSONWebToken-Core.package/JWAHMACSHA256.class/class/checkSignature.withKey..st
@@ -0,0 +1,10 @@
+sign
+checkSignature: parts withKey: key
+	(self
+		signMessage:
+			($.
+				join:
+					{parts first.
+					parts second}) withKey: key)
+		= parts third base64Padded base64Decoded asByteArray
+		ifFalse: [ Error signal: 'signature does not match' ]
\ No newline at end of file
diff --git a/source/JSONWebToken-Core.package/JWANone.class/class/checkSignature.withKey..st b/source/JSONWebToken-Core.package/JWANone.class/class/checkSignature.withKey..st
new file mode 100644
index 0000000..1b3e167
--- /dev/null
+++ b/source/JSONWebToken-Core.package/JWANone.class/class/checkSignature.withKey..st
@@ -0,0 +1,3 @@
+sign
+checkSignature: parts withKey: key
+	
\ No newline at end of file
diff --git a/source/JSONWebToken-Core.package/JWARSASHA256.class/class/checkSignature.withKey..st b/source/JSONWebToken-Core.package/JWARSASHA256.class/class/checkSignature.withKey..st
new file mode 100644
index 0000000..92a361c
--- /dev/null
+++ b/source/JSONWebToken-Core.package/JWARSASHA256.class/class/checkSignature.withKey..st
@@ -0,0 +1,15 @@
+sign
+checkSignature: parts withKey: key
+	| jwtHeaderAndPayload signatureByteArray rsa pubKey |
+	jwtHeaderAndPayload := $.
+		join:
+			{parts first.
+			parts second}.
+	signatureByteArray := parts third base64Padded base64Decoded
+		asByteArray.
+	rsa := LcRSA fromRsaPublicKeyPemString: key.
+	pubKey := LcEvpPublicKey setRSA: rsa.
+
+			(pubKey
+				digestVerifyMessage: jwtHeaderAndPayload
+				with: signatureByteArray) ifFalse: [ Error signal: 'signature does not match' ]
\ No newline at end of file
diff --git a/source/JSONWebToken-Core.package/JWARSASHA256.class/class/signMessage.withKey..st b/source/JSONWebToken-Core.package/JWARSASHA256.class/class/signMessage.withKey..st
deleted file mode 100644
index c48d300..0000000
--- a/source/JSONWebToken-Core.package/JWARSASHA256.class/class/signMessage.withKey..st
+++ /dev/null
@@ -1,3 +0,0 @@
-sign
-signMessage: aString withKey: anObject
-	self notYetImplemented 
\ No newline at end of file
diff --git a/source/JSONWebToken-Core.package/JsonWebSignature.class/instance/checkSignature..st b/source/JSONWebToken-Core.package/JsonWebSignature.class/instance/checkSignature..st
index 4219a18..d74e82f 100644
--- a/source/JSONWebToken-Core.package/JsonWebSignature.class/instance/checkSignature..st
+++ b/source/JSONWebToken-Core.package/JsonWebSignature.class/instance/checkSignature..st
@@ -1,4 +1,5 @@
 signature
 checkSignature: parts
-	((self signatureFor: ($. join: { parts first . parts second })) = parts third base64Padded base64Decoded asByteArray) ifFalse: [
-		Error signal: 'signature does not match' ].
+
+	
+	self protectedHeader algorithm checkSignature: parts withKey: key