Most important change in this CL is that Client is now able to correctly format and sign requests in KID form with a valid "kid" value. According to the RFC, most requests must include KID field in the protected head of JWS requests. The KID value is the account identity provided by the CA during registration. The KID value is also the Account URL. Hence, the CL is tied to account management. Updates golang/go#21081 Change-Id: I13f51e1fc52db7596eb933b47fa2014beb93c1ab Reviewed-on: https://go-review.googlesource.com/c/crypto/+/191602 Run-TryBot: Alex Vaghin <ddos@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>