v4.4.0 - Lyon

New features

• Added the elliptic curve secp256k1 to Crypto.PublicKey.ECC: key generation,
  import and export, ECDSA with Crypto.Signature.DSS, and ECDH with
  Crypto.Protocol.DH.
• Added the mode 'sec1' to Crypto.Signature.DSS.new, for randomized ECDSA on all Weierstrass
  curves. Mode 'fips-186-3' does not accept secp256k1, which is not a curve of that standard.
• GH#759: Added the parameter low_s to Crypto.Signature.DSS.new, for ECDSA signatures
  in the low-S form (for all curves): signing normalizes s, and verifying rejects a high s.
• ECDSA signatures in DER encoding are about 5-8x faster.

Resolved issues

• ECC.import_key raised TypeError instead of ValueError for an OpenSSH public key
  with an unsupported curve or key type, or with a malformed body.
• ECC.import_key accepted an OpenSSH key (public or private) whose curve did not match its key type.
• GH#960: In HPKE, a message rejected by unseal() consumed a sequence number, so all later
  messages of that context failed too. The sequence number now only advances when unseal()
  succeeds (RFC 9180, Section 5.2). Thanks to Zulfareen Shaikh.
• In HPKE, a seal() that raised an exception also consumed a sequence number,
  so the receiver could not unseal the messages that followed.