Imports gitlab.com/yawning/obfs4.git/common/csrand gitlab.com/yawning/obfs4.git/common/uniformdh gitlab.com/yawning/obfs4.git/transports/base gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/goptlib Standard library imports bytes crypto/aes crypto/cipher crypto/hmac crypto/sha256 errors io net time