ccall  [srand]
        ccall  [rand]           

        ccall  [srand],1234
        ccall  [rand]           

section '.idata' import data readable writeable

  library kernel,'KERNEL32.DLL',\
          user,'USER32.DLL',\
          msvcrt,'msvcrt.dll'

  import msvcrt,\
         rand,'rand',\
         srand,'srand'       

PROV_RSA_FULL           = 1
CRYPT_VERIFYCONTEXT     = 0f0000000h

proc rand uses ebx,store,length
        local   context:DWORD
        invoke  CryptAcquireContext,addr context,NULL,NULL,PROV_RSA_FULL,CRYPT_VERIFYCONTEXT
        test    eax,eax
        jz      .done
        invoke  CryptGenRandom,[context],[length],[store]
        test    eax,eax
        setz    bl
        invoke  CryptReleaseContext,[context],0
        test    eax,eax
        setz    al
        or      al,bl
        movzx   eax,al
        dec     eax     
    .done:
        ret
endp    

  import advapi,\
          CryptAcquireContext, 'CryptAcquireContextA',\
          CryptGenRandom, 'CryptGenRandom',\
          CryptReleaseContext, 'CryptReleaseContext'      

Important This API is deprecated. New and existing software should start using Cryptography Next Generation APIs. Microsoft may remove this API in future releases.

format PE GUI 4.0
entry start

include 'win32a.inc'

section '.text' code readable executable

proc rand uses ebx,store,length
        invoke  CryptAcquireContext,context,0,0,1,0xF0000000
        test    eax,eax
        jz      .done
        invoke  CryptGenRandom,dword [context],[length],[store]
        test    eax,eax
        setz    bl
        invoke  CryptReleaseContext,dword [context],0
        test    eax,eax
        setz    al
        or      al,bl
        movzx   eax,al
        dec     eax     
    .done:
        ret
endp

  start:
        ;ccall  [srand]
        ;ccall  [rand]
        call    rand
        cinvoke wsprintf,msg,fmt,eax
        invoke  MessageBox,0,msg,title,0x40
        invoke  ExitProcess,0

section '.data' data readable writeable

  msg     rb 32
  fmt     db '%d',0
  title   db 'rand',0
  context dw ?

section '.idata' import readable writeable

  library kernel,'KERNEL32.DLL',\
          user,'USER32.DLL',\
          advapi,'ADVAPI32.DLL',\
          msvcrt,'msvcrt.dll'

  import kernel,\
         ExitProcess,'ExitProcess'

  import user,\
         wsprintf,'wsprintfA',\
         MessageBox,'MessageBoxA'

  import advapi,\
          CryptAcquireContext, 'CryptAcquireContextA',\
          CryptGenRandom, 'CryptGenRandom',\
          CryptReleaseContext, 'CryptReleaseContext'

;  import msvcrt,\
;         rand,'rand',\
;         srand,'srand'      
    

stdcall rand, buffer, length    

If you use win32ax.inc then the other stuff you had trouble with should be okay.

And it is a stdcall function, not a normal call. So call it like this:

Code:

stdcall rand, buffer, length    

stdcall rand, buffer, 32       

  buffer  rb 32
          db 0      

It really is random data, i.e. different set of data each time I run the program.

// calculate a 't' value that will linearly interpolate from 0 to 1 and back every 20 seconds
DWORD currentTime = GetTickCount();
if ( m_startTime == 0 )
{
    m_startTime = currentTime;
}
float t = 2 * (( currentTime - m_startTime) % 20000) / 20000.0f;
if (t > 1.0f)
{
    t = 2 - t;
}    

##seed $a3b195354a39b70d

::rand | -- rand
  seed $da942042e4dd58b5 * 1 + dup 'seed ! ;

    

seed dq $a3b195354a39b70d

rand:   ;    call rand ; rax a rand number
    mov rax,[seed]
    imul rax,$da942042e4dd58b5
    add rax,1
    mov [seed],rax
    ret

    

   rdtsc    

   rdtsc
   mov bl,10
   mul bl
   mov bl,0xFF
   div bl    

rdrand    

rdrand

   rdtsc
   mov bl,11
   mul bl
   xor dx,dx
   mov bx,0x0100
   div bx 
    

Nobody trusts rdrand anyway. It is a blackbox function with no way to verify it has no backdoors.