cram_secret

# File lib/net/smtp.rb, line 797
    def cram_secret(secret, mask)
      secret = Digest::MD5.digest(secret) if secret.size > CRAM_BUFSIZE
      buf = secret.ljust(CRAM_BUFSIZE, "\0")
      0.upto(buf.size - 1) do |i|
        buf[i] = (buf[i].ord ^ mask).chr
      end
      buf
    end