diff --git a/jwt/jwt.go b/jwt/jwt.go
index 0870fa8..5c34f76 100644
--- a/jwt/jwt.go
+++ b/jwt/jwt.go
@@ -22,7 +22,7 @@ func Decode(jwt string) (Decoded, error) {
 
 	header, err := jws.DecodeHeader(parts[0])
 	if err != nil {
-		return Decoded{}, err
+		return Decoded{}, fmt.Errorf("malformed JWT. Failed to decode header: %w", err)
 	}
 
 	claimsBytes, err := base64.RawURLEncoding.DecodeString(parts[1])
@@ -41,11 +41,17 @@ func Decode(jwt string) (Decoded, error) {
 		return Decoded{}, fmt.Errorf("malformed JWT. Failed to decode signature: %w", err)
 	}
 
+	signerDid, err := did.Parse(header.KID)
+	if err != nil {
+		return Decoded{}, fmt.Errorf("malformed JWT. Failed to parse signer DID: %w", err)
+	}
+
 	return Decoded{
 		Header:    header,
 		Claims:    claims,
 		Signature: signature,
 		Parts:     parts,
+		SignerDID: signerDid,
 	}, nil
 }
 
@@ -134,6 +140,7 @@ type Decoded struct {
 	Claims    Claims
 	Signature []byte
 	Parts     []string
+	SignerDID did.DID
 }
 
 // Verify verifies a JWT (JSON Web Token)
diff --git a/jwt/jwt_test.go b/jwt/jwt_test.go
index 554513d..da8cbf8 100644
--- a/jwt/jwt_test.go
+++ b/jwt/jwt_test.go
@@ -114,3 +114,30 @@ func Test_Decode_Empty(t *testing.T) {
 	assert.Error(t, err)
 	assert.Equal(t, jwt.Decoded{}, decoded)
 }
+
+func Test_Decode_Works(t *testing.T) {
+	vcJwt := `eyJhbGciOiJFZERTQSIsImtpZCI6ImRpZDpqd2s6ZXlKcmRIa2lPaUpQUzFBaUxDSmpjbllpT2lKRlpESTFOVEU1SWl3aWVDSTZJbkY0VjFGS2F6RTJSbWhCZWtOQlRsRktaR1F5UTFkRldrcE9lbXBSYjNGSmRYWk5SbUpVWjFKTVNFRWlmUSMwIiwidHlwIjoiSldUIn0.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.VwvrU5Lmv3rn9rzXB0OCxe-MtE5R0876pXsXNLRuQjoqSNB5tBv_12NqrobwA-LkMzFwzdQ5-LWJni6grGdXCQ`
+	decoded, err := jwt.Decode(vcJwt)
+	assert.NoError(t, err)
+	assert.Equal(t, decoded.Header.ALG, "EdDSA")
+	assert.Equal(t, decoded.Header.KID, "did:jwk:eyJrdHkiOiJPS1AiLCJjcnYiOiJFZDI1NTE5IiwieCI6InF4V1FKazE2RmhBekNBTlFKZGQyQ1dFWkpOempRb3FJdXZNRmJUZ1JMSEEifQ#0")
+	assert.NotZero(t, decoded.SignerDID)
+}
+
+func Test_Decode_Bad_Header(t *testing.T) {
+	vcJwt := `kakaHeader.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.VwvrU5Lmv3rn9rzXB0OCxe-MtE5R0876pXsXNLRuQjoqSNB5tBv_12NqrobwA-LkMzFwzdQ5-LWJni6grGdXCQ`
+	_, err := jwt.Decode(vcJwt)
+	assert.Error(t, err)
+}
+
+func Test_Decode_Bad_Signature(t *testing.T) {
+	vcJwt := `eyJhbGciOiJFZERTQSIsImtpZCI6ImRpZDpqd2s6ZXlKcmRIa2lPaUpQUzFBaUxDSmpjbllpT2lKRlpESTFOVEU1SWl3aWVDSTZJbkY0VjFGS2F6RTJSbWhCZWtOQlRsRktaR1F5UTFkRldrcE9lbXBSYjNGSmRYWk5SbUpVWjFKTVNFRWlmUSMwIiwidHlwIjoiSldUIn0.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.kakaSignature`
+	_, err := jwt.Decode(vcJwt)
+	assert.Error(t, err)
+}
+
+func Test_Decode_HeaderKID_InvalidDID(t *testing.T) {
+	vcJwt := `eyJhbGciOiJFZERTQSIsImtpZCI6Imtha2EiLCJ0eXAiOiJKV1QifQ.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.VwvrU5Lmv3rn9rzXB0OCxe-MtE5R0876pXsXNLRuQjoqSNB5tBv_12NqrobwA-LkMzFwzdQ5-LWJni6grGdXCQ`
+	_, err := jwt.Decode(vcJwt)
+	assert.Error(t, err)
+}
\ No newline at end of file
diff --git a/web5-spec b/web5-spec
index 4c06416..35f3dcf 160000
--- a/web5-spec
+++ b/web5-spec
@@ -1 +1 @@
-Subproject commit 4c064165858a89850db9631a3197940ef32c788e
+Subproject commit 35f3dcf7bfe321d92eb7d55a039fc139ef22097a