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