digsig.txt: standardize document format

Each text file under Documentation follows a different
format. Some doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:

- comment the internal index;
- use the proper markups for titles;
- mark literal blocks.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/digsig.txt

@@ -1,13 +1,20 @@
+==================================
 Digital Signature Verification API
+==================================
 
-CONTENTS
+:Author: Dmitry Kasatkin
+:Date: 06.10.2011
+
+
+.. CONTENTS
 
    1. Introduction
    2. API
    3. User-space utilities
 
 
-1. Introduction
+Introduction
+============
 
 Digital signature verification API provides a method to verify digital signature.
 Currently digital signatures are used by the IMA/EVM integrity protection subsystem.
@@ -17,7 +24,7 @@ GnuPG multi-precision integers (MPI) library. The kernel port provides
 memory allocation errors handling, has been refactored according to kernel
 coding style, and checkpatch.pl reported errors and warnings have been fixed.
 
-Public key and signature consist of header and MPIs.
+Public key and signature consist of header and MPIs::
 
 	struct pubkey_hdr {
 		uint8_t		version;	/* key format version */
@@ -43,9 +50,10 @@ Such approach insures that key or signature header could not be changed.
 It protects timestamp from been changed and can be used for rollback
 protection.
 
-2. API
+API
+===
 
-API currently includes only 1 function:
+API currently includes only 1 function::
 
 	digsig_verify() - digital signature verification with public key
 
@@ -67,7 +75,8 @@ API currently includes only 1 function:
 	int digsig_verify(struct key *keyring, const char *sig, int siglen,
 			  const char *data, int datalen);
 
-3. User-space utilities
+User-space utilities
+====================
 
 The signing and key management utilities evm-utils provide functionality
 to generate signatures, to load keys into the kernel keyring.
@@ -75,7 +84,7 @@ Keys can be in PEM or converted to the kernel format.
 When the key is added to the kernel keyring, the keyid defines the name
 of the key: 5D2B05FC633EE3E8 in the example bellow.
 
-Here is example output of the keyctl utility.
+Here is example output of the keyctl utility::
 
 	$ keyctl show
 	Session Keyring
@@ -90,7 +99,3 @@ Session Keyring
 	$ keyctl list 128198054
 	1 key in keyring:
 	620789745: --alswrv     0     0 user: 5D2B05FC633EE3E8
-
-
-Dmitry Kasatkin
-06.10.2011