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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)[/rouge].
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[/rouge], 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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