;******************************************************************* ; ENIGMA.ASM ; Intelligent Parallel-port encryption dongle based on a 3-rotor ; German WWII Enigma machine algorithm ; ; Professor M. Csele, Niagara College, Canada ; http://technology.niagarac.on.ca/people/mcsele/Enigma.html ; ; Revision History: ; 1.0 - 2003/12/12, Original version for use with MPASM 2.1 ; 1.1 - 2007/04/26, Updated for MPLAB 7.5x (new CONFIG) ;******************************************************************* ; Target: PIC16F84 MCU Assembler/IDE: MPLAB 7.5x ; ; Hardware: ; Port B ; RB0 - RB4 Plaintext character Input 0x00 to 0x2F. ; RB5 Hi/Lo nibble select: Lo=Lo nibble, Hi=Hi nibble ; RB6 Ready output - high indicates code is available ; RB7 Strobe Input - High causes conversion to begin ; ; Port A ; RA0 - RA4 Ciphertext character Output 0x00 to 0x2F. ; Remember to add a 2K2 pull-up resistor to RA4 ; ; Notes: ; Input and output characters are not ASCII but rather a simple code ; where 0x00 represents 'A' and 0x19 (25 dec) represents 'Z'. The ; Enigma only supports characters A-Z. ;******************************************************************* ; Define type of processor to use and include file of standard EQUs ; LIST P=16F84 include "P16F84.INC" ;Configuration - RC Oscillator, WDT Off, PowerUp On __CONFIG _CP_OFF&_WDT_OFF&_RC_OSC&_PWRTE_ON ;Define Registers Used Rotor1Position equ 11 ;Incremental pointers to calculate as Rotor2Position equ 12 ;rotors rotate after each character Rotor3Position equ 13 ;enciphered (Offset) InputRotorPosition equ 14 ;Actual computed rotor positions InputRotorResult equ 15 TempRotorPosition equ 16 ;Actual computed rotor positions TempRotorResult equ 17 Rotor1Output equ 20 ;Actual output from rotor prior to mapping w/offset Rotor2Output equ 21 ;Actual output from rotor prior to mapping w/offset Rotor3Output equ 22 ;Actual output from rotor prior to mapping w/offset ;Define Port B Lines Used HI_NIBBLE equ 5 ;Input. Lo=Lo 4 bits, Hi=Hi 4 bits STROBE equ 7 ;Output. Lo->Hi starts conversion READY equ 6 ;Hi=ready/data available org 0 goto main ;Jump over rotor tables ;Rotor Tables: these act to transpose characters as did the mechanical ; rotors in the original machine Rotor1Forward addwf PCL,f retlw .14 ;Char 0 mapping retlw .15 ;Char 1 mapping retlw .7 ;Char 2 mapping retlw .9 ;Char 3 mapping retlw .24 ;Char 4 mapping retlw .16 ;Char 5 mapping retlw .18 ;Char 6 mapping retlw .8 ;Char 7 mapping retlw .17 ;Char 8 mapping retlw .0 ;Char 9 mapping retlw .10 ;Char 10 mapping retlw .21 ;Char 11 mapping retlw .6 ;Char 12 mapping retlw .2 ;Char 13 mapping retlw .19 ;Char 14 mapping retlw .25 ;Char 15 mapping retlw .4 ;Char 16 mapping retlw .5 ;Char 17 mapping retlw .1 ;Char 18 mapping retlw .23 ;Char 19 mapping retlw .12 ;Char 20 mapping retlw .22 ;Char 21 mapping retlw .13 ;Char 22 mapping retlw .20 ;Char 23 mapping retlw .11 ;Char 24 mapping retlw .3 ;Char 25 mapping Rotor2Forward addwf PCL,f retlw .19 ;Char 0 mapping retlw .16 ;Char 1 mapping retlw .12 ;Char 2 mapping retlw .15 ;Char 3 mapping retlw .24 ;Char 4 mapping retlw .1 ;Char 5 mapping retlw .7 ;Char 6 mapping retlw .6 ;Char 7 mapping retlw .3 ;Char 8 mapping retlw .20 ;Char 9 mapping retlw .2 ;Char 10 mapping retlw .5 ;Char 11 mapping retlw .9 ;Char 12 mapping retlw .10 ;Char 13 mapping retlw .21 ;Char 14 mapping retlw .22 ;Char 15 mapping retlw .13 ;Char 16 mapping retlw .4 ;Char 17 mapping retlw .8 ;Char 18 mapping retlw .11 ;Char 19 mapping retlw .14 ;Char 20 mapping retlw .25 ;Char 21 mapping retlw .23 ;Char 22 mapping retlw .17 ;Char 23 mapping retlw .0 ;Char 24 mapping retlw .18 ;Char 25 mapping Rotor3Forward addwf PCL,f retlw .2 ;Char 0 mapping retlw .25 ;Char 1 mapping retlw .13 ;Char 2 mapping retlw .5 ;Char 3 mapping retlw .23 ;Char 4 mapping retlw .0 ;Char 5 mapping retlw .10 ;Char 6 mapping retlw .18 ;Char 7 mapping retlw .9 ;Char 8 mapping retlw .14 ;Char 9 mapping retlw .11 ;Char 10 mapping retlw .3 ;Char 11 mapping retlw .7 ;Char 12 mapping retlw .20 ;Char 13 mapping retlw .4 ;Char 14 mapping retlw .19 ;Char 15 mapping retlw .16 ;Char 16 mapping retlw .6 ;Char 17 mapping retlw .8 ;Char 18 mapping retlw .17 ;Char 19 mapping retlw .12 ;Char 20 mapping retlw .24 ;Char 21 mapping retlw .22 ;Char 22 mapping retlw .1 ;Char 23 mapping retlw .21 ;Char 24 mapping retlw .15 ;Char 25 mapping Reflector addwf PCL,f retlw .23 ;Reflecting Rotor mapping to 0 retlw .11 ;Reflecting Rotor mapping to 1 retlw .5 ;Reflecting Rotor mapping to 2 retlw .12 ;Reflecting Rotor mapping to 3 retlw .8 ;Reflecting Rotor mapping to 4 retlw .2 ;Reflecting Rotor mapping to 5 retlw .7 ;Reflecting Rotor mapping to 6 retlw .6 ;Reflecting Rotor mapping to 7 retlw .4 ;Reflecting Rotor mapping to 8 retlw .14 ;Reflecting Rotor mapping to 9 retlw .16 ;Reflecting Rotor mapping to 10 retlw .1 ;Reflecting Rotor mapping to 11 retlw .3 ;Reflecting Rotor mapping to 12 retlw .18 ;Reflecting Rotor mapping to 13 retlw .9 ;Reflecting Rotor mapping to 14 retlw .24 ;Reflecting Rotor mapping to 15 retlw .10 ;Reflecting Rotor mapping to 16 retlw .25 ;Reflecting Rotor mapping to 17 retlw .13 ;Reflecting Rotor mapping to 18 retlw .21 ;Reflecting Rotor mapping to 19 retlw .22 ;Reflecting Rotor mapping to 20 retlw .19 ;Reflecting Rotor mapping to 21 retlw .20 ;Reflecting Rotor mapping to 22 retlw .0 ;Reflecting Rotor mapping to 23 retlw .15 ;Reflecting Rotor mapping to 24 retlw .17 ;Reflecting Rotor mapping to 25 Rotor1Reverse addwf PCL,f retlw .9 ;Char 0 mapping for reverse rotor retlw .18 ;Char 1 mapping for reverse rotor retlw .13 ;Char 2 mapping for reverse rotor retlw .25 ;Char 3 mapping for reverse rotor retlw .16 ;Char 4 mapping for reverse rotor retlw .17 ;Char 5 mapping for reverse rotor retlw .12 ;Char 6 mapping for reverse rotor retlw .2 ;Char 7 mapping for reverse rotor retlw .7 ;Char 8 mapping for reverse rotor retlw .3 ;Char 9 mapping for reverse rotor retlw .10 ;Char 10 mapping for reverse rotor retlw .24 ;Char 11 mapping for reverse rotor retlw .20 ;Char 12 mapping for reverse rotor retlw .22 ;Char 13 mapping for reverse rotor retlw .0 ;Char 14 mapping for reverse rotor retlw .1 ;Char 15 mapping for reverse rotor retlw .5 ;Char 16 mapping for reverse rotor retlw .8 ;Char 17 mapping for reverse rotor retlw .6 ;Char 18 mapping for reverse rotor retlw .14 ;Char 19 mapping for reverse rotor retlw .23 ;Char 20 mapping for reverse rotor retlw .11 ;Char 21 mapping for reverse rotor retlw .21 ;Char 22 mapping for reverse rotor retlw .19 ;Char 23 mapping for reverse rotor retlw .4 ;Char 24 mapping for reverse rotor retlw .15 ;Char 25 mapping for reverse rotor Rotor2Reverse addwf PCL,f retlw .24 ;Char 0 mapping for reverse rotor retlw .5 ;Char 1 mapping for reverse rotor retlw .10 ;Char 2 mapping for reverse rotor retlw .8 ;Char 3 mapping for reverse rotor retlw .17 ;Char 4 mapping for reverse rotor retlw .11 ;Char 5 mapping for reverse rotor retlw .7 ;Char 6 mapping for reverse rotor retlw .6 ;Char 7 mapping for reverse rotor retlw .18 ;Char 8 mapping for reverse rotor retlw .12 ;Char 9 mapping for reverse rotor retlw .13 ;Char 10 mapping for reverse rotor retlw .19 ;Char 11 mapping for reverse rotor retlw .2 ;Char 12 mapping for reverse rotor retlw .16 ;Char 13 mapping for reverse rotor retlw .20 ;Char 14 mapping for reverse rotor retlw .3 ;Char 15 mapping for reverse rotor retlw .1 ;Char 16 mapping for reverse rotor retlw .23 ;Char 17 mapping for reverse rotor retlw .25 ;Char 18 mapping for reverse rotor retlw .0 ;Char 19 mapping for reverse rotor retlw .9 ;Char 20 mapping for reverse rotor retlw .14 ;Char 21 mapping for reverse rotor retlw .15 ;Char 22 mapping for reverse rotor retlw .22 ;Char 23 mapping for reverse rotor retlw .4 ;Char 24 mapping for reverse rotor retlw .21 ;Char 25 mapping for reverse rotor Rotor3Reverse addwf PCL,f retlw .5 ;Char 0 mapping for reverse rotor retlw .23 ;Char 1 mapping for reverse rotor retlw .0 ;Char 2 mapping for reverse rotor retlw .11 ;Char 3 mapping for reverse rotor retlw .14 ;Char 4 mapping for reverse rotor retlw .3 ;Char 5 mapping for reverse rotor retlw .17 ;Char 6 mapping for reverse rotor retlw .12 ;Char 7 mapping for reverse rotor retlw .18 ;Char 8 mapping for reverse rotor retlw .8 ;Char 9 mapping for reverse rotor retlw .6 ;Char 10 mapping for reverse rotor retlw .10 ;Char 11 mapping for reverse rotor retlw .20 ;Char 12 mapping for reverse rotor retlw .2 ;Char 13 mapping for reverse rotor retlw .9 ;Char 14 mapping for reverse rotor retlw .25 ;Char 15 mapping for reverse rotor retlw .16 ;Char 16 mapping for reverse rotor retlw .19 ;Char 17 mapping for reverse rotor retlw .7 ;Char 18 mapping for reverse rotor retlw .15 ;Char 19 mapping for reverse rotor retlw .13 ;Char 20 mapping for reverse rotor retlw .24 ;Char 21 mapping for reverse rotor retlw .22 ;Char 22 mapping for reverse rotor retlw .4 ;Char 23 mapping for reverse rotor retlw .21 ;Char 24 mapping for reverse rotor retlw .1 ;Char 25 mapping for reverse rotor main movlw b'10111111' ;Make Port B all inputs except RB6 tris PORTB ; using the TRIState command movlw 0 ;Make Port A all outputs tris PORTA clrf Rotor1Position ;Start at 'AAA' rotor position clrf Rotor2Position clrf Rotor3Position bcf PORTB,READY ;Not Ready loop ;Ensure STROBE is LOW to catch Lo->Hi transition btfsc PORTB,STROBE goto loop bsf PORTB,READY ;Ready to accept data / last data available ;indicated only after strobe goes low ;Wait for STROBE to go high to start next encipher WaitForHiStrobe btfss PORTB,STROBE goto WaitForHiStrobe bcf PORTB,READY ;Busy processing ;Look Up plaintext char at Port B (5 LSB lines) movf PORTB,w andlw b'00011111' ;ROTOR 1 FORWARD ;Step 1) Map the INPUT char to the rotor input terminal ;Add Offset (Rotor1Position) to the input in Mod-26 addwf Rotor1Position,w movwf InputRotorPosition ;Save result movlw .26 subwf InputRotorPosition,w movwf InputRotorResult ;If original position(pointer) was < 26 then the result is <0 ;so use the original value which is in range 0-25 btfsc InputRotorResult,7 ;If result is negative, original goto Rotor1PositionOk ; was <26 so just use it ;If the original was >26 it is NOW mod-26 (<26). Use that instead movf InputRotorResult,w movwf InputRotorPosition Rotor1PositionOk ;Step 2) Transpose character via the rotor itself movf InputRotorPosition,w call Rotor1Forward ;Transpose in forward direction movwf Rotor1Output ;Step 3) Map the rotor output terminal to the correct char ;Subtract the offset from the output terminal in MOD-26 movf Rotor1Position,w subwf Rotor1Output,w ;w=Output-w movwf TempRotorResult ;If negative, process as mod-26 by adding 26 to negative result btfss TempRotorResult,7 goto Rotor1OutputMappedOk addlw .26 ;e.g. 0xFF(-1)+.26=.25 movwf TempRotorResult Rotor1OutputMappedOk ;DONE! Input char is mapped by rotor and rotor position movf TempRotorResult,w ;ROTOR 2 FORWARD ;Step 1) Map the INPUT char to the rotor input terminal ;Add Offset (Rotor2Position) to the input in Mod-26 addwf Rotor2Position,w movwf InputRotorPosition ;Save result movlw .26 subwf InputRotorPosition,w movwf InputRotorResult ;If original position(pointer) was < 26 then the result is <0 ;so use the original value which is in range 0-25 btfsc InputRotorResult,7 ;If result is negative, original goto Rotor2PositionOk ; was <26 so just use it ;If the original was >26 it is NOW mod-26 (<26). Use that instead movf InputRotorResult,w movwf InputRotorPosition Rotor2PositionOk ;Step 2) Transpose character via the rotor itself movf InputRotorPosition,w call Rotor2Forward ;Transpose in forward direction movwf Rotor2Output ;Step 3) Map the rotor output terminal to the correct char ;Subtract the offset from the output terminal in MOD-26 movf Rotor2Position,w subwf Rotor2Output,w ;w=Output-w movwf TempRotorResult ;If negative, process as mod-26 by adding 26 to negative result btfss TempRotorResult,7 goto Rotor2OutputMappedOk addlw .26 ;e.g. 0xFF(-1)+.26=.25 movwf TempRotorResult Rotor2OutputMappedOk ;DONE! Input char is mapped by rotor and rotor position movf TempRotorResult,w ;ROTOR 3 FORWARD ;Step 1) Map the INPUT char to the rotor input terminal ;Add Offset (Rotor3Position) to the input in Mod-26 addwf Rotor3Position,w movwf InputRotorPosition ;Save result movlw .26 subwf InputRotorPosition,w movwf InputRotorResult ;If original position(pointer) was < 26 then the result is <0 ;so use the original value which is in range 0-25 btfsc InputRotorResult,7 ;If result is negative, original goto Rotor3PositionOk ; was <26 so just use it ;If the original was >26 it is NOW mod-26 (<26). Use that instead movf InputRotorResult,w movwf InputRotorPosition Rotor3PositionOk ;Step 2) Transpose character via the rotor itself movf InputRotorPosition,w call Rotor3Forward ;Transpose in forward direction movwf Rotor3Output ;Step 3) Map the rotor output terminal to the correct char ;Subtract the offset from the output terminal in MOD-26 movf Rotor3Position,w subwf Rotor3Output,w ;w=Output-w movwf TempRotorResult ;If negative, process as mod-26 by adding 26 to negative result btfss TempRotorResult,7 goto Rotor3OutputMappedOk addlw .26 ;e.g. 0xFF(-1)+.26=.25 movwf TempRotorResult Rotor3OutputMappedOk ;DONE! Input char is mapped by rotor and rotor position movf TempRotorResult,w ;REFLECT enciphered code back into the rotors for reverse pass call Reflector ;ROTOR 3 REVERSE ;Same process as used for forward except reverse transpose table ;Step 1) Map the INPUT char to the rotor output terminal ;Add Offset (Rotor3Position) to the input in Mod-26 addwf Rotor3Position,w movwf InputRotorPosition ;Save result movlw .26 subwf InputRotorPosition,w movwf InputRotorResult ;If original position(pointer) was < 26 then the result is <0 ;so use the original value which is in range 0-25 btfsc InputRotorResult,7 ;If result is negative, original goto Rotor3RevPositionOk ; was <26 so just use it ;If the original was >26 it is NOW mod-26 (<26). Use that instead movf InputRotorResult,w movwf InputRotorPosition Rotor3RevPositionOk ;Step 2) Transpose character via the rotor itself movf InputRotorPosition,w call Rotor3Reverse ;Transpose in reverse direction movwf Rotor3Output ;Step 3) Map the rotor input terminal to the correct char ;Subtract the offset from the output terminal in MOD-26 movf Rotor3Position,w subwf Rotor3Output,w ;w=Output-w movwf TempRotorResult ;If negative, process as mod-26 by adding 26 to negative result btfss TempRotorResult,7 goto Rotor3RevOutputMappedOk addlw .26 ;e.g. 0xFF(-1)+.26=.25 movwf TempRotorResult Rotor3RevOutputMappedOk ;DONE! Input char is mapped by rotor and rotor position movf TempRotorResult,w ;ROTOR 2 REVERSE ;Same process as used for forward except reverse transpose table ;Step 1) Map the INPUT char to the rotor output terminal ;Add Offset (Rotor2Position) to the input in Mod-26 addwf Rotor2Position,w movwf InputRotorPosition ;Save result movlw .26 subwf InputRotorPosition,w movwf InputRotorResult ;If original position(pointer) was < 26 then the result is <0 ;so use the original value which is in range 0-25 btfsc InputRotorResult,7 ;If result is negative, original goto Rotor2RevPositionOk ; was <26 so just use it ;If the original was >26 it is NOW mod-26 (<26). Use that instead movf InputRotorResult,w movwf InputRotorPosition Rotor2RevPositionOk ;Step 2) Transpose character via the rotor itself movf InputRotorPosition,w call Rotor2Reverse ;Transpose in reverse direction movwf Rotor2Output ;Step 3) Map the rotor input terminal to the correct char ;Subtract the offset from the output terminal in MOD-26 movf Rotor2Position,w subwf Rotor2Output,w ;w=Output-w movwf TempRotorResult ;If negative, process as mod-26 by adding 26 to negative result btfss TempRotorResult,7 goto Rotor2RevOutputMappedOk addlw .26 ;e.g. 0xFF(-1)+.26=.25 movwf TempRotorResult Rotor2RevOutputMappedOk ;DONE! Input char is mapped by rotor and rotor position movf TempRotorResult,w ;ROTOR 1 REVERSE ;Same process as used for forward except reverse transpose table ;Step 1) Map the INPUT char to the rotor output terminal ;Add Offset (Rotor1Position) to the input in Mod-26 addwf Rotor1Position,w movwf InputRotorPosition ;Save result movlw .26 subwf InputRotorPosition,w movwf InputRotorResult ;If original position(pointer) was < 26 then the result is <0 ;so use the original value which is in range 0-25 btfsc InputRotorResult,7 ;If result is negative, original goto Rotor1RevPositionOk ; was <26 so just use it ;If the original was >26 it is NOW mod-26 (<26). Use that instead movf InputRotorResult,w movwf InputRotorPosition Rotor1RevPositionOk ;Step 2) Transpose character via the rotor itself movf InputRotorPosition,w call Rotor1Reverse ;Transpose in reverse direction movwf Rotor1Output ;Step 3) Map the rotor input terminal to the correct char ;Subtract the offset from the output terminal in MOD-26 movf Rotor1Position,w subwf Rotor1Output,w ;w=Output-w movwf TempRotorResult ;If negative, process as mod-26 by adding 26 to negative result btfss TempRotorResult,7 goto Rotor1RevOutputMappedOk addlw .26 ;e.g. 0xFF(-1)+.26=.25 movwf TempRotorResult Rotor1RevOutputMappedOk ;DONE! Input char is mapped by rotor and rotor position movf TempRotorResult,w ;Output ciphertext to Port A. Ready indication at start of loop movwf PORTA ;INCREMENT rotors like an odometer on MOD 26 incf Rotor1Position,f movf Rotor1Position,w sublw .26 ;Check if Pointer > 25 btfss STATUS,Z goto Rotor1PositionIncOk clrf Rotor1Position incf Rotor2Position,f movf Rotor2Position,w sublw .26 ;Check if Pointer > 25 btfss STATUS,Z goto Rotor2PositionIncOk clrf Rotor2Position incf Rotor3Position,f movf Rotor3Position,w sublw .26 ;Check if Pointer > 25 btfss STATUS,Z goto Rotor3PositionIncOk clrf Rotor3Position Rotor3PositionIncOk Rotor2PositionIncOk Rotor1PositionIncOk goto loop END