One-time pad

One-time pad is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Implement a One-time pad

Sub-Tasks

• generate the data for a One-time pad (user needs to specify a filename and length)

The important part is to get "true random" numbers, e.g. from /dev/random

• encryption / decryption ( basically the same operation, much like Rot-13 )

For this step, much of Vigenère cipher could be reused,
with the key to be read from the file containing the One-time pad.

• optional: management of One-time pads: list, mark as used, delete, etc.

Somehow, the users needs to keep track which pad to use for which partner.

For example, here is the data from Wikipedia:

ZDXWWW EJKAWO FECIFE WSNZIP PXPKIY URMZHI JZTLBC YLGDYJ 
HTSVTV RRYYEG EXNCGA GGQVRF FHZCIB EWLGGR BZXQDQ DGGIAK 
YHJYEQ TDLCQT HZBSIZ IRZDYS RBYJFZ AIRCWI UCVXTW YKPQMK 
CKHVEX VXYVCS WOGAAZ OUVVON GCNEVR LMBLYB SBDCDC PCGVJX 
QXAUIP PXZQIJ JIUWYH COVWMJ UZOJHL DWHPER UBSRUJ HGAAPR 
CRWVHI FRNTQW AJVWRT ACAKRD OZKIIB VIQGBK IJCWHF GTTSSE 
EXFIPJ KICASQ IOUQTP ZSGXGH YTYCTI BAZSTN JKMFXI RERYWE 

Tcl

Part 1

Get true random numbers, and turn them into strings.

From Tcl'ers wiki "Cryptographically secure random numbers using /dev/urandom"

<lang Tcl>puts "# True random chars for one-time pad"

proc randInt { min max } {

   set randDev [open /dev/urandom rb]
   set random [read $randDev 8]
   binary scan $random H16 random
   set random [expr {([scan $random %x] % (($max-$min) + 1) + $min)}]
   close $randDev
   return $random

}

set alfa "ABCDEFGHIJKLMNOPQRSTUVWXYZ" set len 48 set rs "" for {set i 0} {$i < $len} {incr i} {

 if { [expr {$i % 6} ] == 0} { append rs " " }
 set r [randInt 1 26]
 set char [string index $alfa $r]
 append rs $char

} puts ":$rs." </lang>

Output:

# True random chars for one-time pad
: IDEVVW KCTMY KLKLID DSGKIV WHMOX LIEYWF MCIECW OUQVIV.

Part 2

...