------------------
In addition to the message to be signed, the U2F signature operation
-requires a few additional parameters:
-
- byte control bits (e.g. "user presence required" flag)
- byte[32] SHA256(message)
- byte[32] SHA256(application)
- byte key_handle length
- byte[] key_handle
-
-This signature is signed over a blob that consists of:
+requires the key handle and a few additional parameters. The signature
+is signed over a blob that consists of:
byte[32] SHA256(application)
byte flags (including "user present", extensions present)
byte flags (including "user present")
uint32 counter
- byte[32] ecdsa_signature (in X9.62 format).
+ byte[] ecdsa_signature (in X9.62 format).
For use in the SSH protocol, we wish to avoid server-side parsing of ASN.1
format data in the pre-authentication attack surface. Therefore, the