#summary Introduction to low-level Yubikey C library
#labels Featured,Phase-Deploy

= Introduction =

This package make up the low-level C software development kit for the
Yubico authentication device, the Yubikey.  In particular:

* AUTHORS, COPYING, NEWS, README: meta-information about the project.

* yubikey.h: Prototypes for library.

* ykparse.c, ykmodhex.c, ykhex.c, ykcrc.c, ykaes.c: Library implementation.

* selftest.c: Library self tests.

* ykdebug.c: Command line tool to print debug information about a token.

* modhex.c: Command-line tool for modhex encoding/decoding.

* simple.mk: Simple makefile to build the above parts.

* configure.ac, Makefile.am: Autoconf/Automake files.

== Building from SVN ==

Skip to the next section if you are using an official packaged
version, which is what we recommend.

You may check out the sources using SVN with the following command:

{{{
  svn checkout http://yubico-c.googlecode.com/svn/trunk/ yubico-c
}}}

This will create a directory 'yubico-c'.  Enter the directory:

{{{
  cd yubico-c
}}}

Autoconf, automake and libtool must be installed.

Generate the build system using:

{{{
  autoreconf --install
}}}

= Building =

To build using the Autoconf, automake and libtool infrastructure,
which is recommend for more advanced purposes especially for
cross-compilation and shared library support, build it as follows.

{{{
$ ./configure
$ make check install
}}}

Another way to build the package is by running 'make -f simple.mk
check'.  It will build each component, and also test it.  See below
for sample session.  This is useful if you want to target a platform
that doesn't support Autoconf/automake/libtool well.

{{{
jas@mocca:~/src/yubico-c$ make -f simple.mk  check
cc -I. -Wall -g   -c -o ykparse.o ykparse.c
cc -I. -Wall -g   -c -o ykmodhex.o ykmodhex.c
cc -I. -Wall -g   -c -o ykhex.o ykhex.c
cc -I. -Wall -g   -c -o ykcrc.o ykcrc.c
cc -I. -Wall -g   -c -o ykaes.o ykaes.c
cc -I. -Wall -g    modhex.c ykparse.o ykmodhex.o ykhex.o ykcrc.o ykaes.o yubikey.h   -o modhex
cc -I. -Wall -g    ykdebug.c ykparse.o ykmodhex.o ykhex.o ykcrc.o ykaes.o yubikey.h   -o ykdebug
cc -I. -Wall -g    selftest.c ykparse.o ykmodhex.o ykhex.o ykcrc.o ykaes.o yubikey.h   -o selftest
selftest.c: In function ‘main’:
selftest.c:65: warning: pointer targets in passing argument 1 of ‘yubikey_aes_decrypt’ differ in signedness
selftest.c:65: warning: pointer targets in passing argument 2 of ‘yubikey_aes_decrypt’ differ in signedness
./selftest
modhex-encode("test") = ifhgieif
Modhex-1 success
modhex-decode("ifhgieif") = test
Modhex-2 success
hex-encode("test") = 74657374
Hex-1 success
hex-decode("74657374") = test
Hex-2 success
aes-decrypt (data=0123456789abcdef, key=abcdef0123456789)
 => 838a467f34639551755bd32a4a2f15e1
AES-1 success
jas@mocca:~/src/yubico-c$ 
}}}

= Command-line tools =

Two command line tools, modex and ykdebug, are included.

The "modhex" program converts data between modhex, normal hex, and
binary form.

The "ykdebug" program decrypts and parses one OTP given the OTP and
the AES key corresponding to that Yubikey.

{{{
$ ./modhex test
ifhgieif
$ ./modhex -d ifhgieif
test
$ ./modhex -h b565716f
nghgibhv
$ ./modhex -h -d nghgibhv
b565716f
$ ./ykdebug ecde18dbe76fbd0c33330f1c354871db dteffujedcflcindvdbrblehecuitvjkjevvehjd
warning: overlong token, ignoring prefix: dteffuje
Input:
  token: dcflcindvdbrblehecuitvjkjevvehjd
          20 4a 07 b2 f2 1c 1a 36 30 e7 df 89 83 ff 36 82 
  aeskey: urtubjtnuihvntcreeeecvbregfjibtn
          ec de 18 db e7 6f bd 0c 33 33 0f 1c 35 48 71 db 
Output:
          87 92 eb fe 26 cc 13 00 a8 c0 00 10 b4 08 6f 5b 

Struct:
  uid: 87 92 eb fe 26 cc 
  counter: 19 (0x0013)
  timestamp (low): 49320 (0xc0a8)
  timestamp (high): 0 (0x00)
  session use: 16 (0x10)
  random: 2228 (0x8b4)
  crc: 23407 (0x5b6f)

Derived:
  cleaned counter: 19 (0x0013)
  modhex uid: jikdunvudhrr
  triggered by caps lock: no
  crc: F0B8
  crc check: ok
$ ./ykdebug ecde18dbe76fbd0c33330f1c354871db dteffujehknhfjbrjnlnldnhcujvddbikngjrtgh
warning: overlong token, ignoring prefix: dteffuje
Input:
  token: hknhfjbrjnlnldnhcujvddbikngjrtgh
          69 b6 48 1c 8b ab a2 b6 0e 8f 22 17 9b 58 cd 56 
  aeskey: urtubjtnuihvntcreeeecvbregfjibtn
          ec de 18 db e7 6f bd 0c 33 33 0f 1c 35 48 71 db 
Output:
          87 92 eb fe 26 cc 13 00 30 c2 00 11 c8 9f 23 c8 

Struct:
  uid: 87 92 eb fe 26 cc 
  counter: 19 (0x0013)
  timestamp (low): 49712 (0xc230)
  timestamp (high): 0 (0x00)
  session use: 17 (0x11)
  random: 40904 (0x9fc8)
  crc: 51235 (0xc823)

Derived:
  cleaned counter: 19 (0x0013)
  modhex uid: jikdunvudhrr
  triggered by caps lock: no
  crc: F0B8
  crc check: ok
$ 
}}}

= Questions? =

Talk to <simon@yubico.com>.