This adds SealAnonymous and OpenAnonymous functions that implement the libsodium "sealed box" functionality. Fixes golang/go#35346 Change-Id: I22455f1b83595ec8a68d1861e635bd6cb0573f44 GitHub-Last-Rev: 7d334cf861942ec63ad613b7f28fb6dd7a1f9992 GitHub-Pull-Request: golang/crypto#107 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/205241 Reviewed-by: Filippo Valsorda <filippo@golang.org> Run-TryBot: Filippo Valsorda <filippo@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>