}

    #
    # NOTE: The fallback URN, relative to the base URI, where the Package
    #       Signing Keys may be downloaded.  This should only be used when
    #       the primary URN did not produce valid data.
    #
    variable openPgpKeyUrnFallback1; # DEFAULT: pkg_keys_mirror_1

    if {$force || ![info exists openPgpKeyUrnFallback1]} then {
      set openPgpKeyUrnFallback1 pkg_keys_mirror_1
    }

    #
    # NOTE: The URN, relative to the base URI, where a login request may
    #       be sent.
    #
    variable loginUrn; # DEFAULT: pkgd_login

    #
    # NOTE: The fallback URI where the Package Signing Keys may be
    #       downloaded.  This should return a payload containing the OpenPGP
    #       key data.  This should only be used when the primary URN did not
    #       produce valid OpenPGP key data.
    #
    variable openPgpKeyUriFallback; # DEFAULT: .../${openPgpKeyUrnFallback1}

    if {$force || ![info exists openPgpKeyUriFallback]} then {
      set openPgpKeyUriFallback {${baseUri}/${openPgpKeyUrnFallback1}}
    }

    #
    # NOTE: The URI where a login request may be sent.  This should return a
    #       payload containing the necessary HTTP(S) cookie information.
    #
    variable loginUri; # DEFAULT: ${baseUri}/${loginUrn}?...

  #       a letter.
  #
  # <public>
  proc useServerId { {serverId ""} } {
    variable downloadUrn
    variable loginUrn
    variable logoutUrn
    variable openPgpKeyUrn
    variable openPgpKeyUrnFallback1
    variable platformsUrn

    ::PackageRepository::verifyServerId $serverId

    if {[string length $serverId] > 0} then {
      #
      # NOTE: Reset the URN variables to values that should cause
      #       the specified server Id to be used (assume the server
      #       Id itself is valid and active).
      #
      # HACK: These prefixes are hard-coded and must be manually kept
      #       synchronized with those in the setupDownloadServerVars
      #       procedure.
      #
      set downloadUrn [appendArgs pkgd_file_ $serverId]
      set loginUrn [appendArgs pkgd_login_ $serverId]
      set logoutUrn [appendArgs pkgd_logout_ $serverId]
      set openPgpKeyUrn [appendArgs pkg_keys_ $serverId]
      set openPgpKeyUrnFallback1 [appendArgs pkg_keys_mirror_1_ $serverId]
      set platformsUrn [appendArgs pkgd_platforms_ $serverId]
    } else {
      #
      # NOTE: Forcibly reset URN variables to their default values.
      #
      setupDownloadServerVars true
    }
  }

  #
  # <internal>
  proc downloadAndSaveOpenPgpKeyFile { fileName } {
    variable baseUri
    variable openPgpKeyUri
    variable openPgpKeyUriFallback
    variable openPgpKeyUrn
    variable openPgpKeyUrnFallback1

    set errors [list]

    foreach substUri [list $openPgpKeyUri $openPgpKeyUriFallback] {
      #
      # NOTE: Attempt to download the Package Signing Keys using the
      #       configured URI.