Ask HN: Is derivating passwords from a master key and service name a good idea?

  import hashlib
  import base64
  
  def password(masterkey, service):
      h = hashlib.sha256() # probably could use hashlib.hmac?
      h.update(bytearray(masterkey, "utf-8"))
      h.update(bytearray(service, "utf-8"))
      return base64.b85encode(h.digest()).decode("utf-8") # With Base85 and SHA256 we'll get passwords of 40 characters including numbers, letters and some special chars
  
  key = "&T{TEeN_\q9+-L9_"
  
  print(password(key, "hackernews"))  # "kLh4WhHTC^M*$uko=plAViC{J;%WJ)9`jlo&-`cS" will be used as my HN password
  print(password(key, "facebook"))    # "0B+37p0n@JKP)b>nz}yfJ%#Qy*^d+gsQRwF08S}Q" will be used as my facebook password
  print(password(key, "twitter"))     # "SeR$P!-Z_z%%J5NI0qtO@5Y#$`K-d*7glNC%w=EQ" will be used as my twitter password