Newsgroup: it.comp.sicurezza.crittografia
Titolo: [Announce] Attack against OpenPGP encryption

Save gente,
stavo leggendo le news di gnupg e sono "incappato" su questo post?
Qualcuno ne sa qualcosa?
[...]
David Shaw dshaw at 
jabberwocky.com
Fri Feb 11 02:00:17 CET 2005
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il link e' questo:
http://lists.gnupg.org/pipermail/gnupg-announce/2005q1/000190.html
Bye
Joe

 
http://lists.gnupg.org/pipermail/gnupg-announce/2005q1/000190.html
Darei quasi per certo che qualcuno ha fatto il "mattacchione" e ha
mandato un messaggio (peraltro senza scriverci neanche NIENTE a parte il
subject -_-) allarmante in mailing list gnupg-announce, facendo finta di
essere David Shaw...
- --
L a p o   L u c h i n i
l a p o @ l a p o . i t
w w w . l a p o . i t /
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j+oAniEGC+R6D2697BFhwUiYIkKRllNx
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(seguire tutto il thread che n'è scaturito)
Ciao,
un TJL73 che si chiede se c'è altro modo per accedere a quelle liste...
-- 
"Per ogni problema complesso,
 c'e` sempre una soluzione semplice. Ed e` sbagliata."
                                                  -- George Bernard Shaw

 un TJL73 che si chiede se c'č altro modo per accedere a quelle liste...
La cosa che mi pare piů RIDICOLA č che quel emssaggio nno leggibile č
perfino linkato dall'homepage!!!!!!!
Peraltro č similmente illeggibile ANCHE il messaggio da te linkato, ora
voglio supporre che sia un problema "che c'č a tratti", nno che tu
stesso sia caduto nel medesimo "problema" di cui stavamo proprio in quel
momento parlando, no?
un Lapo perplesso e stupefatto
- --
L a p o   L u c h i n i
l a p o @ l a p o . i t
w w w . l a p o . i t /
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http://enigmail.mozdev.org
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  [X.509 available]
Linux Reg. User: #263663 / Machine: #216144 (Arch Linux/Wombat)
On the Web: 
http://www.quagliata.eu.org
 - My GPG Key:0x5539D8E4
On ICQ: 48618109 - On Jabber: 
qu...@jabber.org/@jabber.linux.it
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opRNm5M4OqmQOAha9Bqqpfo=
=yu89
-----END PGP SIGNATURE-----

  [X.509 available]
Linux Reg. User: #263663 / Machine: #216144 (Arch Linux/Wombat)
On the Web: 
http://www.quagliata.eu.org
 - My GPG Key:0x5539D8E4
On ICQ: 48618109 - On Jabber: 
qu...@jabber.org/@jabber.linux.it
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=tr+Q
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nel ng <gmane.comp.gnu.gnupg.users> (l'accesso è anonimo).
Se volete, lo posso postare qui in formato RAW con tutto il testo
completo, le patch e la firma. Come preferite.
Ciao,
un TJL73 che, dopo lunga ed estenuante ricerca, n'è venuto a capo...
-- 
"Ho visto cose... che, voi umani... neanche immaginate."

,
|     <mailto:
gnupg-use...@gnupg.org
?subject=subscribe>
| Original-Sender: 
gnupg-use...@gnupg.org
| Errors-To: 
gnupg-use...@gnupg.org
| Xref: 
main.gmane.org
 gmane.comp.gnu.gnupg.users:6025
| X-Report-Spam: 
http://spam.gmane.org/gmane.comp.gnu.gnupg.users:6025
|
|
| --===============1473521360==
| Content-Type: multipart/signed; micalg=pgp-sha1;
|     protocol="application/pgp-signature"; boundary="IMjqdzrDRly81ofr"
| Content-Disposition: inline
|
|
| --IMjqdzrDRly81ofr
| Content-Type: multipart/mixed; boundary="oJ71EGRlYNjSvfq7"
| Content-Disposition: inline
|
|
| --oJ71EGRlYNjSvfq7
| Content-Type: text/plain; charset=us-ascii
| Content-Disposition: inline
|
| Last night, Serge Mister and Robert Zuccherato published a paper
| reporting on an attack against OpenPGP symmetric encryption.
|
| This attack, while very significant from a cryptographic point of
| view, is not generally effective in the real world.  To be specific,
| unless you have your OpenPGP program set up as part of an automated
| system to accept encrypted messages, decrypt them, and then provide a
| response to the submitter, then this does not affect you at all.
|
| There is a very good writeup on the attack that goes into more depth
| at 
http://www.pgp.com/library/ctocorner/openpgp.html
|
| There will undoubtedly be further discussion of this over the next
| several days, but I wanted to provide a few comments now, to try and
| answer some questions that may arise:
|
| 1) This is not a bug in any particular OpenPGP implementation (GnuPG,
|    PGP, Hushmail, etc).  Rather, this is an attack against the OpenPGP
|    protocol itself.
|
| 2) The attack requires an average of 32,768 probes to get two bytes of
|    plaintext.  This is why it is completely ineffective against
|    human beings, who will presumably wonder why a stranger wants them
|    to decrypt thousands and thousands of messages that won't decrypt,
|    and then tell them what errors were seen.
|
| 3) It might be effective against an automated process that
|    incorporates OpenPGP decryption, if that process returns errors
|    back to the sender.
|
| 4) The OpenPGP Working Group will be discussing this issue and coming
|    up with an effective and permanent fix.  In the meantime, I have
|    attached two patches to this mail.  These patches disable a
|    portion of the OpenPGP protocol that the attack is exploiting.
|    This change should not be user visible.  With the patch in place,
|    this attack will not work using a public-key encrypted message.  It
|    will still work using a passphrase-encrypted message.  These
|    patches will be part of the 1.2.8 and 1.4.1 releases of GnuPG.
|
| 5) The full paper is available at 
http://eprint.iacr.org/2005/033
|    It's a great piece of work.
|
| David
|
| --oJ71EGRlYNjSvfq7
| Content-Type: text/plain; charset=us-ascii
| Content-Disposition: attachment; filename="gnupg-1.2.7.cfb.patch"
| Content-Transfer-Encoding: quoted-printable
|
| Index: include/cipher.h
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
| RCS file: /cvs/gnupg/gnupg/include/cipher.h,v
| retrieving revision 1.53.2.6
| diff -u -r1.53.2.6 cipher.h
| --- include/cipher.h    29 Nov 2004 21:07:43 -0000  1.53.2.6
| +++ include/cipher.h    8 Feb 2005 04:12:12 -0000
| @@ -76,6 +76,7 @@
|      int keylen;
|      int algo_info_printed;
|      int use_mdc;
| +    int symmetric;
|      byte key[32]; /* this is the largest used keylen (256 bit) */
|  } DEK;
| =20
| Index: g10/mainproc.c
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
| RCS file: /cvs/gnupg/gnupg/g10/mainproc.c,v
| retrieving revision 1.112.2.27
| diff -u -r1.112.2.27 mainproc.c
| --- g10/mainproc.c  27 Jun 2004 18:26:49 -0000  1.112.2.27
| +++ g10/mainproc.c  8 Feb 2005 04:12:13 -0000
| @@ -317,6 +317,8 @@
|     c->dek =3D passphrase_to_dek( NULL, 0, algo, &enc->s2k, 0, NULL, NULL );
|     if(c->dek)
|       {
| +       c->dek->symmetric=3D1;
| +
|         /* FIXME: This doesn't work perfectly if a symmetric key
|            comes before a public key in the message - if the user
|            doesn't know the passphrase, then there is a chance
| Index: g10/encr-data.c
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
| RCS file: /cvs/gnupg/gnupg/g10/encr-data.c,v
| retrieving revision 1.29
| diff -u -r1.29 encr-data.c
| --- g10/encr-data.c 29 Jun 2002 13:46:33 -0000  1.29
| +++ g10/encr-data.c 8 Feb 2005 04:12:14 -0000
| @@ -120,7 +120,7 @@
|      cipher_sync( dfx.cipher_hd );
|      p =3D temp;
|  /* log_hexdump( "prefix", temp, nprefix+2 ); */
| -    if( p[nprefix-2] !=3D p[nprefix] || p[nprefix-1] !=3D p[nprefix+1] ) {
| +    if( dek->symmetric && (p[nprefix-2] !=3D p[nprefix] || p[nprefix-1] !=
| =3D p[nprefix+1]) ) {
|     rc =3D G10ERR_BAD_KEY;
|     goto leave;
|      }
|
| --oJ71EGRlYNjSvfq7
| Content-Type: text/plain; charset=us-ascii
| Content-Disposition: attachment; filename="gnupg-1.4.0.cfb.patch"
| Content-Transfer-Encoding: quoted-printable
|
| Index: include/cipher.h
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
| RCS file: /cvs/gnupg/gnupg/include/cipher.h,v
| retrieving revision 1.63
| diff -u -r1.63 cipher.h
| --- include/cipher.h    29 Nov 2004 21:14:18 -0000  1.63
| +++ include/cipher.h    8 Feb 2005 04:10:29 -0000
| @@ -75,6 +75,7 @@
|      int keylen;
|      int algo_info_printed;
|      int use_mdc;
| +    int symmetric;
|      byte key[32]; /* this is the largest used keylen (256 bit) */
|  } DEK;
| =20
| Index: g10/mainproc.c
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
| RCS file: /cvs/gnupg/gnupg/g10/mainproc.c,v
| retrieving revision 1.161
| diff -u -r1.161 mainproc.c
| --- g10/mainproc.c  21 Oct 2004 19:18:47 -0000  1.161
| +++ g10/mainproc.c  8 Feb 2005 04:10:30 -0000
| @@ -330,6 +330,8 @@
| =20
|         if(c->dek)
|           {
| +       c->dek->symmetric=3D1;
| +
|         /* FIXME: This doesn't work perfectly if a symmetric
|            key comes before a public key in the message - if
|            the user doesn't know the passphrase, then there is
| Index: g10/encr-data.c
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
| =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
| RCS file: /cvs/gnupg/gnupg/g10/encr-data.c,v
| retrieving revision 1.30
| diff -u -r1.30 encr-data.c
| --- g10/encr-data.c 8 Oct 2004 21:54:26 -0000   1.30
| +++ g10/encr-data.c 8 Feb 2005 04:10:30 -0000
| @@ -125,7 +125,7 @@
|      cipher_sync( dfx.cipher_hd );
|      p =3D temp;
|  /* log_hexdump( "prefix", temp, nprefix+2 ); */
| -    if( p[nprefix-2] !=3D p[nprefix] || p[nprefix-1] !=3D p[nprefix+1] ) {
| +    if( dek->symmetric && (p[nprefix-2] !=3D p[nprefix] || p[nprefix-1] !=
| =3D p[nprefix+1]) ) {
|     rc =3D G10ERR_BAD_KEY;
|     goto leave;
|      }
|
| --oJ71EGRlYNjSvfq7--
|
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| --===============1473521360==
| Content-Type: text/plain; charset="us-ascii"
| MIME-Version: 1.0
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| Content-Disposition: inline
|
| _______________________________________________
| Gnupg-announce mailing list
| 
Gnupg-a...@gnupg.org
| 
http://lists.gnupg.org/mailman/listinfo/gnupg-announce
|
| --===============1473521360==
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| _______________________________________________
| Gnupg-users mailing list
| 
Gnupg...@gnupg.org
| 
http://lists.gnupg.org/mailman/listinfo/gnupg-users
|
| --===============1473521360==--
`-----
That's all, folks.
Ciao,
un TJL73 che inoltra così come ha trovato...
-- 
"Sono stato coinvolto in un buon esempio di contraccezione orale.
 Ho chiesto a una ragazza di venire a letto con me
 e lei mi ha detto di no."
                                                          -- Woody Allen