[SwiftStriker00]

I was toying around with this concept of encryption, and thought it would be fun to share with everyone in the form of the challenge. I coded it in java, and providing .class files to help you decode it, so that is why I stuck it in the Java Challenge forum.

The Challenge
Decode the following messages

• 061009240930 1830142409240325
  
• 0020 09301710 03241410000010050020110502300310
  
• 06301824 03200324 20300040 042005401410 162406201524 003000401635
  
• 161015241624 1224062414001510

Some Support
Did you think I would leave you completely in the dark? Of course not. Attached to this post is a Challenge.class file. It has three methods available to you. main(), test(), and guess().

Usage: Challenge <challenge> <solution>

You may run the main without args to get a command line interface walk through while solving the challenges or you can input the same parameters as the test() (see below) to get an answer right away

test( int challenge, String solution )

challenge - the number of the challenge you are trying to solve
solution - your solution to the challenge

guess( String input, String solution )

input - the cleartext message
solution - the encoded message
Hints
Need a little extra help? I will give you some vague hints to possibly point you in the right direction to the design of this code.

Spoiler

Are you sure?

OK, Hint 1:

Spoiler

4

Hint 2:

Spoiler

Clock

Hint 3:

Spoiler

Military Time

Hint 4:

Spoiler

In order to determine the time, minutes often rely on the hours to get an accurate result

Hint 5:

Spoiler

How many minutes past the hour when the big hand is on the 2?

Hint 6:

Spoiler

Punctuation is such an Odd word.

A note about the Challenge class
when you download the file, remove the .txt extension. I only did this to upload to </d.i.c>

Attached File(s)

•  Challenge.class.txt (5.97K)
  Number of downloads: 174

[CasiOo]

Got the answer for the two first ones at least. I can write up how I found the solutions inside spoiler tags if anyone is interested.

This post has been edited by CasiOo: 16 February 2012 - 05:06 AM

[SwiftStriker00]

Please do, I am curious to see how you went about it, and how it may differ from the design. Also if you got the first too, shouldnt be hard to get the next two. Did you use any hints?

18240630 00201524 16240610 181001241000152416101424 00300424 16240610 152016100035

This post has been edited by SwiftStriker00: 16 February 2012 - 07:49 AM

[GunnerInc]

I kinda cheated. I decompiled the class file to see what the characters were. :-)
Then I created 2 lookup tables with those characters - 1 for the hours, 1 for the mins.

Looped through the string grabbing 2 characters at a time, converted the string number to a DWORD, then used that number for the index in the lookup table.

Did it in Assembly if you are interested.

[GunnerInc]

SwiftStriker00, on 16 February 2012 - 09:48 AM, said:

18240630 00201524 16240610 181001241000152416101424 00300424 16240610 152016100035

Missed that one,

Spoiler

skyhawk133

silly

This post has been edited by GunnerInc: 19 February 2012 - 10:53 AM

[GunnerInc]

Java forum, yes, but my solution in Assembly since I like challenges:

Spoiler

.data
Hours           db  "*", "b", "c", "d", "f" 
                db  "g", "h", "j", "k", "l" 
                db  "m", "n", "p", "q", "r"
                db  "s", "t", "v", "w", "x"
                db  "y", "z", "ß", "@"

Mins            db  "a", 0, 0, 0, 0
                db  ".", 0, 0, 0, 0
                db  "e", 0, 0, 0, 0
                db  ",", 0, 0, 0, 0
                db  "i", 0, 0, 0, "*"
                db  "!", 0, 0, 0, 0
                db  "o", 0, 0, 0, 0
                db  "?", 0, 0, 0, 0
                db  "u", 0, 0, 0, 0
                db  "\", 0, 0, 0, 0
                db  "0", "1", "2", "3", "4"
                db  "5", "6", "7", "8", "9"

Chal1           db  "061009240930 1830142409240325", 0
CHAL1_SIZE      equ $ - Chal1 - 1

Chal2           db  "0020 09301710 03241410000010050020110502300310", 0   
CHAL2_SIZE      equ $ - Chal2 - 1

Chal3           db  "06301824 03200324 20300040 042005401410 162406201524 003000401635", 0    
CHAL3_SIZE      equ $ - Chal3 - 1

Chal4           db  "161015241624 1224062414001510", 0
CHAL4_SIZE      equ $ - Chal4 - 1

Extra           db "18240630 00201524 16240610 181001241000152416101424 00300424 16240610 152016100035", 0
EXTRA_SIZE      equ $ - Extra - 1

.data?
Decoded         BYTE    148 dup (?)

.code
start:

    print   offset Chal1, 13, 10
    push    CHAL1_SIZE
    push    offset Chal1
    call    Decode
    print   eax, 13, 10, 13 ,10
    
    print   offset Chal3, 13, 10    
    push    CHAL3_SIZE
    push    offset Chal3
    call    Decode
    print   eax, 13, 10, 13 ,10

    print   offset Chal4, 13, 10
    push    CHAL4_SIZE
    push    offset Chal4
    call    Decode
    print   eax, 13, 10, 13 ,10

    print   offset Extra, 13, 10
    push    EXTRA_SIZE
    push    offset Extra
    call    Decode
    print   eax, 13, 10
    
    inkey "Press the", ' "any key to"', " quit"
    exit

Decode: 
    enter   4, 0
    mov     esi, [ebp + 8]              ; challenge encoded string pointer
    mov     dword ptr [ebp - 4], 0      ; zero out temp buffer
    lea     ebx, Decoded                ; pointer to decoded buffer

_Hours:
    lea     edi, Hours                  ; hours lookup table
    mov     ax, word ptr[esi]           ; get 2 bytes (hours) from string
    add     esi, 2                      ; increase encoded string pointer
    mov     word ptr[ebp - 4], ax       ; mov to temp buffer
    lea     eax, [ebp - 4]              ; load address of temp buffer
    push    eax                         ;
    call    atodw                       ; convert
    
    mov     al, byte ptr [edi + eax]    ; get char from hours lookup table
    cmp     al, "*"                     ; skip these chars                  
    je      @F                          ;            
    cmp     al, "ß"                     ;
    je      @F                          ;
    cmp     al, "@"                     ;
    je      @F                          ;
    
    mov     byte ptr [ebx], al          ; save char to decoded buffer
    inc     ebx                         ; increase decoded buffer pointer index
    
@@:
    sub     dword ptr[ebp + 12], 2      ; decrease string length counter
    ; ##### Could add a check for space here
    
_Mins:
    lea     edi, Mins                   ; mins lookup table
    mov     ax, word ptr[esi]           ; get 2 bytes (mins) from string 
    add     esi, 2                      ; increase encoded string pointer
    mov     word ptr[ebp - 4], ax       ; mov to temp buffer
    lea     eax, [ebp - 4]              ; load address of temp buffer    
    push    eax                         ;
    call    atodw                       ; convert

    mov     al, byte ptr [edi + eax]    ; get char from mins lookup table
    cmp     al, "*"                     ; Skip these chars
    je      @F                          ;
    
    mov     byte ptr [ebx], al          ; save to decoded buffer
    inc     ebx                         ; increase decoded buffer pointer index

@@:
    sub     dword ptr[ebp + 12], 2      ; decrease string length counter
    jz      DecodeDone                  ; zero? yup, we are done
    
    mov     al, byte ptr[esi]           ; get next character
    cmp     al, 32                      ; is it a space?
    jne     _Hours                      ; No

    mov     byte ptr [ebx], 32          ; yes, save to decoded buffer
    inc     ebx                         ; increase decoded buffer pointer index
    inc     esi                         ; increase encoded string pointer                     
    sub     dword ptr[ebp + 12],  1     ; decrease string length counter
    jmp     _Hours
    
DecodeDone:    
    mov     byte ptr [ebx], 0           ; zero terminate string
    mov     eax, offset Decoded
    leave
    ret     4 * 2
end start

Once I figure out your algo to encrypt it, I will write an Encrypt function.

This post has been edited by GunnerInc: 19 February 2012 - 12:16 PM

[SwiftStriker00]

Actually I love the Assembly approach. And I don't know if you cheated, because I could have protected the code more, I was curious to see if people would have taken that route instead of looking for the pattern.

This post has been edited by SwiftStriker00: 21 February 2012 - 09:11 AM

[GunnerInc]

I could add a few checks to it, like if the string in is an odd number of characters then add padding to the end, add a check for spaces in more spots and a few other things. ATM, it relies on a properly formated encoded string. But the idea you have is interesting. I will keep playing around with it.

[GunnerInc]

Ok, had time to work on the encode function. Pass this through your decoder and let me know what it says, if it is correct, I will comment my code and post it, in Assembly of course :-)

1624060011240824 20300040 04301424 16240610 0224060009240910112405100015 0020 06000324 04401125

[SwiftStriker00]

Spoiler

thank you for the challenge, i had fun!

Your welcome!

[GunnerInc]

Ok, as promised here is the code and a console app to test with. I overly commented it. It is MASM source but I took the long way, so it should be easy to convert to another Assembler. I did cheat and used a few MASM macros to get console input and print to console. Hope someone can learn from it and join us on the "Dark Side" MWAHAHAHAHAHAHAAA!!!!!

Attached File(s)

•  EncodeDecode24.zip (4.98K)
  Number of downloads: 57