@Daniel : thanks!!!
On Thu, Jul 25, 2019 at 4:11 PM Daniel Kahn Gillmor <d...@fifthhorseman.net> wrote: > On Thu 2019-07-25 14:00:08 -0400, Kynn Jones via Gnupg-users wrote: > > The GnuPG documentation refers to an "INTEROPERABILITY WITH > > OTHER OPENPGP PROGRAMS section", but when I search for this > > title, I find only references to it, not the actual section. > > > > Does any one know where that section is? > > It appears to be in the info page, which (on my system) i can access > with "info gpg" and then searching for "interoperability". In the > manual page (gpg(1), accessed via "man 1 gpg") the section is titled > just "INTEROPERABILITY" (why this difference between info and man? I > don't know or understand!) > > I reproduce the current version out of info (from 2.2.17) below. > > Regards, > > --dkg > > INTEROPERABILITY WITH OTHER OPENPGP PROGRAMS > ******************************************** > > GnuPG tries to be a very flexible implementation of the OpenPGP > standard. In particular, GnuPG implements many of the optional parts of > the standard, such as the SHA-512 hash, and the ZLIB and BZIP2 > compression algorithms. It is important to be aware that not all > OpenPGP programs implement these optional algorithms and that by forcing > their use via the '--cipher-algo', '--digest-algo', > '--cert-digest-algo', or '--compress-algo' options in GnuPG, it is > possible to create a perfectly valid OpenPGP message, but one that > cannot be read by the intended recipient. > > There are dozens of variations of OpenPGP programs available, and > each supports a slightly different subset of these optional algorithms. > For example, until recently, no (unhacked) version of PGP supported the > BLOWFISH cipher algorithm. A message using BLOWFISH simply could not be > read by a PGP user. By default, GnuPG uses the standard OpenPGP > preferences system that will always do the right thing and create > messages that are usable by all recipients, regardless of which OpenPGP > program they use. Only override this safe default if you really know > what you are doing. > > If you absolutely must override the safe default, or if the > preferences on a given key are invalid for some reason, you are far > better off using the '--pgp6', '--pgp7', or '--pgp8' options. These > options are safe as they do not force any particular algorithms in > violation of OpenPGP, but rather reduce the available algorithms to a > "PGP-safe" list. >
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