diff --git a/model/signature.proto b/model/signature.proto
index 6bc355d..9d6fe37 100644
--- a/model/signature.proto
+++ b/model/signature.proto
@@ -11,4 +11,19 @@ enum SignatureType {
     BitcoinSignature = 1;
     // in bytes: []byte{2,0,0,0} for multisig validation purpose only
     MultisigSignature = 2;
+}
+
+// BitcoinPrivateKeyBytesLength represent the length of private key that can use
+enum PrivateKeyBytesLength {
+    PrivateKeyInvalid = 0;
+    PrivateKey256Bits =32;
+    PrivateKey384Bits = 48;
+    PrivateKey512Bits = 64;
+}
+
+// BitcoinPublicKeyFormat represent the option of the Bitcoin public key format that can use
+//  public key format : https://bitcoin.org/en/wallets-guide#public-key-formats
+enum BitcoinPublicKeyFormat {
+    PublicKeyFormatUncompressed = 0;
+    PublicKeyFormatCompressed = 1;
 }
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