added nuclear random numbers

rdoetjes · rdoetjes · commit 7940db00da04 · 2024-06-01T09:17:53.000+02:00
diff --git a/nuclear_random/README.md b/nuclear_random/README.md
@@ -0,0 +1,21 @@
+# NUCLEAR RANDOM NUMBERS DEMO
+The code in @main.asm is a program written in assembly language for the Commodore 64 computer. Its purpose is to generate truly random bytes using the decay events of a radioactive isotope as a source of entropy.
+
+The program does not take any direct input from the user. Instead, it relies on the decay events of a radioactive isotope, which are detected by a Geiger counter connected to the Commodore 64's joystick port. When a decay event occurs, it triggers a pulse that simulates a button press on the joystick.
+
+The output of the program is an array of 255 random bytes, stored in memory starting at address $2000 (8192 decimal). These random bytes are generated by sampling the least significant bit (LSB) of a free-running timer (Timer B) whenever a decay event is detected.
+
+Here's how the program achieves its purpose:
+
+The program sets up Timer B to count CPU clock cycles and starts it running.
+It then enters a loop where it waits for a decay event to occur, which is detected by checking for a simulated button press on the joystick port.
+When a decay event is detected, the program reads the LSB of Timer B and shifts it into a temporary byte.
+After 8 bits have been shifted into the temporary byte, it is stored in the random_bytes array, and the process starts over for the next byte.
+This process is repeated until all 255 bytes in the random_bytes array have been filled.
+The key logic flow and data transformation happening in the program are:
+
+The program continuously monitors the joystick port for a simulated button press, which indicates a decay event.
+When a decay event is detected, the LSB of Timer B is read and shifted into a temporary byte.
+After 8 bits have been shifted into the temporary byte, it is stored in the random_bytes array, and the process starts over for the next byte.
+This process is repeated until all 255 bytes in the random_bytes array have been filled.
+The program uses a free-running timer (Timer B) to avoid relying on system entropy, which could potentially be predictable or influenced by external factors. By sampling the timer's value at the precise moment of a decay event, which is a truly random quantum event, the program ensures that the generated bytes are truly random and unpredictable.
diff --git a/nuclear_random/main.asm b/nuclear_random/main.asm
@@ -0,0 +1,170 @@
+// The idea is that we have a free running timer that is incremented by the CPU clock. 
+// When a decay happens the joystick button is pressed by a transistor connected between fire button and ground.
+// As the button is pressed the LSB of the timer B is read and shifted into a byte when 8 bits are filled we have
+// a truly random byte generated
+// we actually generate 255 bytes in total, so we can do some analysis on the distribution of the bytes
+// those random bytes start at $2000 (8192)
+// Since we use a free running timer that we read when a decay happens, we avoid system entropy.
+.const CONT_TIMER_B = $DC0F 
+.const LSB_TIMER_B = $DC06 
+.const CURRENT_SCANLINE = $D012
+.const JOYSTICK_2 = $DC00
+.const SCREEN_MEM = $0400
+
+BasicUpstart2(main)
+
+*=$1000
+main:
+    jsr setup
+    jsr start_timer_b
+
+loop:
+    jsr print_bit_pattern
+
+    // the detector has a 10ms pulse so we wait max 40ms for the next decay, so we don't flood the whole byte with same bit 
+    jsr wait_for_raster_line    // give a 20 ms wait
+    jsr wait_for_raster_line    // give a 20 ms wait
+
+    jsr wait_for_decay_pulse    // wait till the isotope decays
+
+    jsr mask_lowest_bit         //mask the lowest bit of timer B and if 1 shift without add if 0 shift with add of 1
+    beq !shift_add_1+           // if 0 shift left and add one
+
+    jsr shift_add_nothing       // if 1 shift left and don't add one
+    beq !back_to_basic+         // if sub routine set Z flag then exit to basic
+
+    jmp loop                    // read the next pulse
+
+!shift_add_1:   
+    jsr shift_add_1             // shift left and add 1 to the intermediate result in random_result byte that offset x points to
+    beq !back_to_basic+         // if subroutine set Z flag then exit to basic
+
+    jmp loop                    // read next bit
+
+//Exit to basic gracefully
+!back_to_basic:
+    sei
+    lda     #$37
+    sta     $01             
+    cli
+    jsr     $ff8a           
+    jsr     $ff81           
+    jsr     $ff84           
+    rts
+
+
+//
+//SUBROUTINES
+//
+
+//sets up the counters
+setup:
+    lda CONT_TIMER_B       // load the configuration of TIMER B	   
+    and #%1000101   // configure to count clock cycles
+    ora #%0000000   // start the timer
+    sta CONT_TIMER_B       // store the timer config and start
+    ldx #$00        // offset ponter into random_bytes array 
+    ldy #$00        // ofset pointer to bit in the random_byte pointed to by random_bytes+x
+    rts
+
+// start the timer B again
+start_timer_b:
+    ora #%00000001      //start timer B again
+    sta CONT_TIMER_B           //set timer B register
+    rts
+ 
+// this waits for raster line ff to give a bit of a delay
+wait_for_raster_line:
+    !wait:
+    lda CURRENT_SCANLINE // read current rasterline
+    cmp $ff              // if current rasterline is not ff than wait
+    bne !wait-
+    rts
+
+// wait for the joystick button (which is triggered by the geiger counter when a isotope decays)
+wait_for_decay_pulse:
+   !await_pulse:
+    //poll joystick button, a button press is a tick from the geiger counter
+    lda JOYSTICK_2      // read joystick 2
+    and #$10            // check button pressed
+    bne !await_pulse-   // no new decay measured than wait
+    rts
+
+// mask the lowerst bit of timer b LSB value
+mask_lowest_bit:
+    lda LSB_TIMER_B           // read lsb of timer B
+    sta SCREEN_MEM+1          // show the low byte timer B on screen
+    and #$1                   // mask lowest bit to see if the timer B count is odd or eveb
+    rts
+
+// shift the value in random_bytes+x left one position
+shift_add_nothing:
+    lda random_bytes,X  // load the current random byte (X is the offset into the 255 random bytes)
+    asl                 // if even just shift result left without adding one to the result
+    jsr prep_for_next_bit // set everything up for the next bit (or next byte)
+    rts
+
+// shidt the value in random_bytes+x left one position and set the lowest bit to 1
+shift_add_1:
+    lda random_bytes,X  // load the current random byte (X is the offset into the 255 random bytes)
+    asl                 // shift the temporary random result left
+    ora #$01            // add one to the result
+    jsr prep_for_next_bit   // set everything up for the next bit (or next byte)
+    rts
+
+//prepare the offset to y for the next bit, if y is 8 then set to 0 and increment x pointer
+prep_for_next_bit:
+    sta random_bytes,X  //store the temporary random byte back into the array   
+    iny                 //increment the bit counter
+    cpy #$08            //if bit counter is 8 then reset bit counter and increment array counter to fill next byte
+    beq !reset_y+       //if y==8 then reset
+    rts
+!reset_y:
+    jsr reset_y         // reset y to 0
+    rts
+
+reset_y:
+    lda random_bytes,X  // get the whole random byte from offset x
+    sta SCREEN_MEM           // show the random byte on screen
+    ldy #$00            // reset the bit counter to 0
+    inx                 // since y was 8, it means we should also increment x to point to the next random byte
+    rts
+
+print_bit_pattern:  
+    // store a and y to the stack
+    pha
+    tya
+    pha
+
+    ldy #%000000001     // load bit pattern to #%000000001
+    sty bit_pattern     // store bit pattern 
+    ror bit_pattern     // set bit pattern to the one in the carry, so the next ror it will be 100000000
+    ldy #8              // 8 bits to print
+
+    !loop:
+    ror bit_pattern     // shift bit to mask, to the right
+    lda random_bytes, X // load the random byte from the array
+    and bit_pattern     // mask the random byte with the bit pattern
+    beq !draw_zero+     //  if the result is 0 then draw a zero
+
+    lda #49             // draw a 1
+    jmp !draw_bit+      // draw the actual 1 bit to the screen
+
+    !draw_zero: 
+    lda #48             // draw a 0
+
+    !draw_bit:
+    sta SCREEN_MEM+2,y         // draw the bit to the screen starting from 402 with offset y
+    dey                 // decrement the bit counter
+    bne !loop-          // if bit counter is not 0 then loop again
+
+    // restore a and y from the stack
+    pla                 
+    tay
+    pla
+    rts
+
+*=$2000 "random bytes"
+// array that holds the 255 random bytes that were generated
+random_bytes: .fill 255,00     
+bit_pattern: .byte 0
diff --git a/nuclear_random/main.dbg b/nuclear_random/main.dbg
@@ -0,0 +1,135 @@
+<C64debugger version="1.0">
+   <Sources values="INDEX,FILE">
+      0,KickAss.jar:/include/autoinclude.asm
+      1,/Users/rdoetjes/develop/nuclear_random/main.asm
+   </Sources>
+
+   <Segment name="Default" dest="" values="START,END,FILE_IDX,LINE1,COL1,LINE2,COL2">
+      <Block name="Basic">
+         $0801,$0802,0,56,2,56,6
+         $0803,$0804,0,57,5,57,9
+         $0805,$0805,0,58,5,58,9
+         $0806,$0809,0,59,2,59,6
+         $080a,$080a,0,60,2,60,6
+         $080b,$080c,0,62,5,62,9
+      </Block>
+      <Block name="Unnamed">
+         $1000,$1002,1,11,5,11,7
+         $1003,$1005,1,12,5,12,7
+         $1006,$1008,1,15,5,15,7
+         $1009,$100b,1,18,5,18,7
+         $100c,$100e,1,19,5,19,7
+         $100f,$1011,1,20,5,20,7
+         $1012,$1014,1,22,5,22,7
+         $1015,$1017,1,24,5,24,7
+         $1018,$1019,1,25,5,25,7
+         $101a,$101c,1,27,5,27,7
+         $101d,$101e,1,28,5,28,7
+         $101f,$1021,1,30,5,30,7
+         $1022,$1024,1,33,5,33,7
+         $1025,$1026,1,34,5,34,7
+         $1027,$1029,1,36,5,36,7
+         $102a,$102a,1,40,5,40,7
+         $102b,$102c,1,41,5,41,7
+         $102d,$102e,1,42,5,42,7
+         $102f,$102f,1,43,5,43,7
+         $1030,$1032,1,44,5,44,7
+         $1033,$1035,1,45,5,45,7
+         $1036,$1038,1,46,5,46,7
+         $1039,$1039,1,47,5,47,7
+         $103a,$103c,1,56,5,56,7
+         $103d,$103e,1,57,5,57,7
+         $103f,$1040,1,58,5,58,7
+         $1041,$1043,1,59,5,59,7
+         $1044,$1045,1,60,5,60,7
+         $1046,$1047,1,61,5,61,7
+         $1048,$1048,1,62,5,62,7
+         $1049,$104a,1,66,5,66,7
+         $104b,$104d,1,67,5,67,7
+         $104e,$104e,1,68,5,68,7
+         $104f,$1051,1,73,5,73,7
+         $1052,$1053,1,74,5,74,7
+         $1054,$1055,1,75,5,75,7
+         $1056,$1056,1,76,5,76,7
+         $1057,$1059,1,82,5,82,7
+         $105a,$105b,1,83,5,83,7
+         $105c,$105d,1,84,5,84,7
+         $105e,$105e,1,85,5,85,7
+         $105f,$1061,1,89,5,89,7
+         $1062,$1064,1,90,5,90,7
+         $1065,$1066,1,91,5,91,7
+         $1067,$1067,1,92,5,92,7
+         $1068,$106a,1,96,5,96,7
+         $106b,$106b,1,97,5,97,7
+         $106c,$106e,1,98,5,98,7
+         $106f,$106f,1,99,5,99,7
+         $1070,$1072,1,103,5,103,7
+         $1073,$1073,1,104,5,104,7
+         $1074,$1075,1,105,5,105,7
+         $1076,$1078,1,106,5,106,7
+         $1079,$1079,1,107,5,107,7
+         $107a,$107c,1,111,5,111,7
+         $107d,$107d,1,112,5,112,7
+         $107e,$107f,1,113,5,113,7
+         $1080,$1081,1,114,5,114,7
+         $1082,$1082,1,115,5,115,7
+         $1083,$1085,1,117,5,117,7
+         $1086,$1086,1,118,5,118,7
+         $1087,$1089,1,121,5,121,7
+         $108a,$108c,1,122,5,122,7
+         $108d,$108e,1,123,5,123,7
+         $108f,$108f,1,124,5,124,7
+         $1090,$1090,1,125,5,125,7
+         $1091,$1091,1,129,5,129,7
+         $1092,$1092,1,130,5,130,7
+         $1093,$1093,1,131,5,131,7
+         $1094,$1095,1,133,5,133,7
+         $1096,$1098,1,134,5,134,7
+         $1099,$109b,1,135,5,135,7
+         $109c,$109d,1,136,5,136,7
+         $109e,$10a0,1,139,5,139,7
+         $10a1,$10a3,1,140,5,140,7
+         $10a4,$10a6,1,141,5,141,7
+         $10a7,$10a8,1,142,5,142,7
+         $10a9,$10aa,1,144,5,144,7
+         $10ab,$10ad,1,145,5,145,7
+         $10ae,$10af,1,148,5,148,7
+         $10b0,$10b2,1,151,5,151,7
+         $10b3,$10b3,1,152,5,152,7
+         $10b4,$10b5,1,153,5,153,7
+         $10b6,$10b6,1,156,5,156,7
+         $10b7,$10b7,1,157,5,157,7
+         $10b8,$10b8,1,158,5,158,7
+         $10b9,$10b9,1,159,5,159,7
+      </Block>
+      <Block name="random bytes">
+         $2000,$20fe,1,163,15,163,19
+         $20ff,$20ff,1,164,14,164,18
+      </Block>
+   </Segment>
+
+   <Labels values="SEGMENT,ADDRESS,NAME,START,END,FILE_IDX,LINE1,COL1,LINE2,COL2">
+      Default,$1000,main,1,10,1,10,5
+      Default,$1006,loop,1,14,1,14,5
+      Default,$103a,setup,1,55,1,55,6
+      Default,$1049,start_timer_b,1,65,1,65,14
+      Default,$104f,wait_for_raster_line,1,71,1,71,21
+      Default,$1057,wait_for_decay_pulse,1,79,1,79,21
+      Default,$105f,mask_lowest_bit,1,88,1,88,16
+      Default,$1068,shift_add_nothing,1,95,1,95,18
+      Default,$1070,shift_add_1,1,102,1,102,12
+      Default,$107a,prep_for_next_bit,1,110,1,110,18
+      Default,$1087,reset_y,1,120,1,120,8
+      Default,$1091,print_bit_pattern,1,127,1,127,18
+      Default,$2000,random_bytes,1,163,1,163,13
+      Default,$20ff,bit_pattern,1,164,1,164,12
+      Default,$080b,upstartEnd,0,61,1,61,11
+   </Labels>
+
+   <Breakpoints values="SEGMENT,ADDRESS,ARGUMENT">
+   </Breakpoints>
+
+   <Watchpoints values="SEGMENT,ADDRESS1,ADDRESS2,ARGUMENT">
+   </Watchpoints>
+
+</C64debugger>
diff --git a/nuclear_random/main.prg b/nuclear_random/main.prg
diff --git a/nuclear_random/main.sym b/nuclear_random/main.sym
@@ -0,0 +1,14 @@
+.label wait_for_raster_line=$104f
+.label shift_add_1=$1070
+.label bit_pattern=$20ff
+.label wait_for_decay_pulse=$1057
+.label main=$1000
+.label reset_y=$1087
+.label start_timer_b=$1049
+.label shift_add_nothing=$1068
+.label loop=$1006
+.label mask_lowest_bit=$105f
+.label setup=$103a
+.label prep_for_next_bit=$107a
+.label random_bytes=$2000
+.label print_bit_pattern=$1091
diff --git a/nuclear_random/main.vs b/nuclear_random/main.vs
@@ -0,0 +1,15 @@
+al C:104f .wait_for_raster_line
+al C:1070 .shift_add_1
+al C:20ff .bit_pattern
+al C:1057 .wait_for_decay_pulse
+al C:80b .upstartEnd
+al C:1000 .main
+al C:1087 .reset_y
+al C:1049 .start_timer_b
+al C:1068 .shift_add_nothing
+al C:1006 .loop
+al C:105f .mask_lowest_bit
+al C:103a .setup
+al C:107a .prep_for_next_bit
+al C:2000 .random_bytes
+al C:1091 .print_bit_pattern
