I used Dr Duh's yubikey setup about 20 days ago with no issue. I ran through it again last night on an M1 Mac with Brew and when we created the expiring authentication key, the keylist shows [AR] for the key where it would normally show just [A] for authentication. I have consulted the man pages on gnu.org and while I can see the other codes (E,S,A) - I see no definition for R. What is R?

This is something like what I see on the list step (copied from Dr Duh's guide and altered to add the R):

$ gpg -K
sec   rsa4096/0xFF3E7D88647EBCDB 2017-10-09 [C]
      Key fingerprint = 011C E16B D45B 27A5 5BA8  776D FF3E 7D88 647E BCDB
uid                            Dr Duh <[email protected]>
ssb   rsa4096/0xBECFA3C1AE191D15 2017-10-09 [S] [expires: 2018-10-09]
ssb   rsa4096/0x5912A795E90DD2CF 2017-10-09 [E] [expires: 2018-10-09]
ssb   rsa4096/0x3F29127E79649A3D 2017-10-09 [AR] [expires: 2018-10-09]

1 Answer 1


I think these letters signify the capabilities. Reading https://github.com/gpg/gnupg/blob/master/doc/DETAILS#field-12---key-capabilities I think the R means "restricted encryption".

With regard to the case difference: "...in addition to these letters, the primary key has uppercase versions of the letters to denote the usable capabilities of the entire key...".

  • I see restricted encryption mentioned in the list archives: lists.gnupg.org/pipermail/gnupg-users/2023-May.txt So I believe you are correct. Should I ask a different question as to what this flag means?
    – lopass
    Commented Jun 13, 2023 at 15:40
  • Well, your question was what the R represents. By going through the source code and the DETAILS doc I gave you the answer. Not sure what "restricted encryption" means exactly... maybe someone else can help you out with that.
    – Edward
    Commented Jun 14, 2023 at 11:28
  • I will give you the answer check and either ask on the mailing list or ask another question
    – lopass
    Commented Jun 14, 2023 at 20:35

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