passwd_encryption_method()
{
  crypt_id="$(
    sudo grep "$1:\$" /etc/shadow |
    sed 's/^[^:]*:$([^$]*)$.*/1/'
  )"
  if test -z "$crypt_id"; then
    echo Cannot find user "$1", or "$1" has no password
    return 1
  fi
  case "$crypt_id" in
    (1) echo MD5;;
    (2a) echo Blowfish;;
    (5) echo SHA-256;;
    (6) echo SHA-512;;
    (*) echo Unknown method, id="$crypt_id";;
  esac
}