diff --git a/src/fido/credential.c b/src/fido/credential.c
index d055ba7..3c2d122 100644
--- a/src/fido/credential.c
+++ b/src/fido/credential.c
@@ -72,6 +72,10 @@ int credential_create(CborCharString *rpId, CborByteString *userId, CborCharStri
             CBOR_CHECK(cbor_encode_text_stringz(&mapEncoder2, "hmac-secret"));
             CBOR_CHECK(cbor_encode_boolean(&mapEncoder2, *extensions->hmac_secret));
         }
+        if (extensions->largeBlobKey == ptrue) {
+            CBOR_CHECK(cbor_encode_text_stringz(&mapEncoder2, "largeBlobKey"));
+            CBOR_CHECK(cbor_encode_boolean(&mapEncoder2, true));
+        }
         CBOR_CHECK(cbor_encoder_close_container(&mapEncoder, &mapEncoder2));
     }
     CBOR_CHECK(cbor_encode_uint(&mapEncoder, 0x08));
@@ -160,6 +164,7 @@ int credential_load(const uint8_t *cred_id, size_t cred_id_len, const uint8_t *r
                     CBOR_FIELD_KEY_TEXT_VAL_BOOL(2, "hmac-secret", cred->extensions.hmac_secret);
                     CBOR_FIELD_KEY_TEXT_VAL_UINT(2, "credProtect", cred->extensions.credProtect);
                     CBOR_FIELD_KEY_TEXT_VAL_BYTES(2, "credBlob", cred->extensions.credBlob);
+                    CBOR_FIELD_KEY_TEXT_VAL_BOOL(2, "largeBlobKeys", cred->extensions.largeBlobKey);
                     CBOR_ADVANCE(2);
                 }
                 CBOR_PARSE_MAP_END(_f1, 2);
diff --git a/src/fido/credential.h b/src/fido/credential.h
index 50fc478..4e4dce7 100644
--- a/src/fido/credential.h
+++ b/src/fido/credential.h
@@ -32,6 +32,7 @@ typedef struct CredExtensions {
     uint64_t credProtect;
     const bool *minPinLength;
     CborByteString credBlob;
+    const bool *largeBlobKey;
     bool present;
 } CredExtensions;
 
@@ -63,5 +64,6 @@ extern void credential_free(Credential *cred);
 extern int credential_store(const uint8_t *cred_id, size_t cred_id_len, const uint8_t *rp_id_hash);
 extern int credential_load(const uint8_t *cred_id, size_t cred_id_len, const uint8_t *rp_id_hash, Credential *cred);
 extern int credential_derive_hmac_key(const uint8_t *cred_id, size_t cred_id_len, uint8_t *outk);
+extern int credential_derive_large_blob_key(const uint8_t *cred_id, size_t cred_id_len, uint8_t *outk);
 
 #endif // _CREDENTIAL_H_