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Home page > II. Pro > 4. Informatique/Computing > PGP for Symbian (updated)

PGP for Symbian (updated)

It works!

13 August 2009, by CeD

Other versions of this article:


For Jolla/Sailfish see here
I installed successfully an old command line MS-DOS version of PGP on a Nokia E90 Communicator (Symbian s60v3) with the s60DosBox emulator (dosbox_s60_20090623 ’full’ version only).
JPG - 235.2 kb
pgp_symbian

Although the em­u­la­tor has lim­i­ta­tions not al­low­ing con­ve­nient in­ter­ac­tive batch­es, this in­stal­la­tion is work­able.

Requirements:

  • Install s60DosBox and its binary dependencies [1]
  • Install (just decompress) PGP 2.6.3i in an ad hoc sub-folder (for instance “PGP”) of the DosBox main folder
  • Adjust the autoexec section of dosbox.conf:
[autoexec]
# Lines in this section will be run at startup.
# map virtkeybmap.txt (instead of premapper.txt) to test virtual keyboard for touch-ui
@echo off
mount c c:\data\dos
mount b e:\b
rem s60map c:/data/premapper.txt
echo please wait while PGP is coming
c:
# NOTES:
# c:\nu below is for Norton Utilities, including NDOS
# c:\ut below is for various MS-DOS utilities you may consider useful
PATH = z:\;c:\ut;c:\nu;c:\pgp
SET PGPPATH=C:\PGP
cls
pgp
type c:\pgp\tips.txt
b:
ndos

  • Adjust PGP’s config.txt:
MyName = "your_name"
Language = en
CharSet = cp850
ArmorLines = 24
Armor = on          # Use -a flag for ASCII armor whenever applicable
TextMode = on       # Attempt to use -t option where applicable
ClearSig = on       # Use ASCII armor even for unencrypted signed messages
Verbose = 2         # Verbose diagnostic messages
ShowPass = on       # Echo password when user types it
Interactive = on    # Interactively prompt the user when adding keys (-ka)
EncryptToSelf = on  # Encrypt all messages with your own public key
TZFix = -9          # Brussels timezone

  • Write some basic batches like these:

cr.bat: (to crypt)

echo Crypt
echo Arg1 = "What" Arg2 = "For whom"
echo Example : cr message recipient
pgp -e %1 %2

un.bat: (to uncrypt)

echo Uncrypt
echo Unique argument = "What"
echo Example : un message.asc
pgp -d %1

si.bat: (to sign with cypher)

echo Sign with cypher
echo Arg1 = "What" Arg2 = "ForWhom" Arg3 = "ByWhom"
echo Example : si message recipient author
pgp -se %1 %2 -u %3

…etc. Refer to pg­p­doc1.txt and pg­p­doc2.txt (sup­plied with PGP 2.6.3i) to write more batch­es.

  • Add a “tips.txt” file in your PGP folder as a reminder of things to remember (depending on the small batches you have written):
--------------------------------------------------
PGP 2.6.3i Symbian s60v3 SIMPLIFIED INSTRUCTIONS:
--------------------------------------------------
Crypt : cr What ForWhom
Conventional cyphering: chx What
Uncrypt : un What
Sign with cypher : si What ToWhom ByWhom
ClearSig : cs What ByWhom
Check : pgp What
Help : pgph
Execute DATE to adjust time stamp
Execute SET PGPPASS=[passphrase of your PGP key]

(As your PGP/MS-DOS ses­sion takes place in RAM, you may safe­ly set the en­vi­ron­ment vari­able “pgp­pass” ev­ery time you start a ses­sion: when you close the em­u­la­tor by press­ing the red key, your passphrase will be erased with­out leav­ing a trace. Of course, do NOT write it in “tips.txt” or in the “au­toex­ec” sec­tion of “dos­box.conf”, as those files are per­sis­tent).

  • Maintain a PC mirror folder of your Symbian PGP folder in order to manage your key rings easily.
  • Do not cypher big files (say 100 Kb or less)
  • Avoid signing documents, as DosBox is unable to manage date and time properly [2]. If you have installed Norton Utilities (see below), launch NDOS and execute DATE every time you start the s60DosBox emulator. Anyway, be aware that the time stamp will not be accurate (the date may be correct, the time will never be true).
  • “RSA Legacy” keys are accepted, not recent keys (“DH/DSS” or “DSA” for instance) generated by PGP v8.xx or GnuPG 2.xx. If you already have one of those new keys, you will need to create a “legacy” RSA key from PGP 2.6.3i and certify it with your main key. Better so: if your key dedicated to mobile privacy is compromised, your main key will not be affected.
  • This international version of PGP (the “i” in “2.6.3i”) generates keys using the IDEA algorithm, which is (or used to be) patent-protected in some countries including France (but not Belgium). For this reason, GnuPG (where anything patented is banned) does not recognize them. Hence, anything cyphered or signed for your ’RSA Legacy’ key by PGP 2.6.3i will be decodable only with PGP 2.6xx, not with GnuPG 2.xx [3]. PGP 8.xx (commercial package) has a downwards compatibility feature allowing to use Legacy keys, even when cyphering/signature was made using PGP 2.6xx. [4]
  • Although this may be a valuable contribution for the Symbian world, which tragically lacks efficient privacy and authentication tools, I consider it just as a temporary solution, until a state-of-the-art tool is released: what users need is an application fully interoperable with current standards, i.e. advanced, robust algorithms (AES, DSA etc.) and completely integrated with the Symbian operating system, including direct call from email, instant messaging, office and SMS applications. The main interest of this post is to produce evidence that running asymmetric cryptography tools IS workable with Symbian s60.
  • The rudimentary workaround described here is certainly improvable. Any suggestion welcome.

Useful read­ing

P.S.

For Jolla/Sailfish see here

Footnotes

[1] On my E90, I could not run the last dos­box_073_s60_20091207_rc2 ver­sion. However, the pre­vi­ous dos­box_s60_20090623 ver­sion is ok (not the ’slim’ one, on­ly the ’full’ one).

[2] There is a -par­tial- workaround: in­stall Norton Utilities’ NDOS, as it un­der­stands the DATE com­mand (not TIME)

[3] However, if cypher­ing and/or sig­na­ture was made us­ing GnuPG with an RSA key, no prob­lem.

[4] Explanation : keys gen­er­at­ed by PGP 2.6.3i can be ex­port­ed to GnuPG; it is able to use them (with­out us­ing the in­fa­mous al­go­rithm) for cypher­ing or sign­ing. But the re­sult of cypher­ing or sig­na­ture made by PGP 2.6.3i with this kind of key will not be de­cod­able by GnuPG, as it will in­volve the in­fa­mous al­go­rithm. It’s a bit com­pli­cat­ed, OK. This is a su­perb il­lus­tra­tion of the so-called “pro­gress” (sic) al­lowed by ’patentabil­i­ty’ of soft­ware, again­st what Europe is re­sist­ing, but half-heart­ed­ly.


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