Other Parts Discussed in Thread: MSP430G2553
Just an example for a G2553, in theory you could skip all the ORG as all unused ISR slots are used up with password enhancers.
As you never know if you later use unused_isr, don't put a reti there but jump (Branch) to a reti to keep same instructions length.
A brute force attack would only take hrs, but they would had to know you use a table.
You could replace nmi_jmp with another a DB 'XY' to make it harder, as that IRQ is least likely that you would later change to being used.
Put some other data you have interleaved with BR table, should make it even harder. don't always use 0xFFA0, ±6 to make it harder.
A virgin chip does not have 0x0000 at 0xFFDE, so always try 0xff,0xff,0xff,0xff... password first so it does not erase infoA
Having your program trying multiple passwords without checking if true is OK. As once in, it stays command unlocked until next reset.
ASEG 0xFFA0 ; shuffle this section once if you want added security PORT1_JMP BR #PORT1_ISR PORT2_JMP BR #PORT2_ISR ADC10_JMP BR #ADC10_ISR USCIAB0TX_JMP BR #USCIAB0TX_ISR USCIAB0RX_JMP BR #USCIAB0RX_ISR TIMER0_A1_JMP BR #TIMER0_A1_ISR TIMER0_A0_JMP BR #TIMER0_A0_ISR WDT_JMP BR #not_used_ISR COMPARATORA_JMP BR #not_used_ISR TIMER1_A1_JMP BR #TIMER1_A1_ISR TIMER1_A0_JMP BR #not_used_ISR NMI_JMP BR #not_used_ISR RESET_JMP BR #main ASEG 0xFFDC DB 0x1,0x20 ; reversion for internal use DW 0x0000 ; zero disables the erasure of the flash if an invalid password is supplied during BSL. COMMON INTVEC /* Interrupt Vector base 0xFFE0 */ DB 'PASW' /* not used, so use it as password enhancer */ ORG PORT1_VECTOR /* 0xFFE4 Port 1 */ DW PORT1_JMP ORG PORT2_VECTOR /* 0xFFE6 Port 2 */ DW PORT2_JMP DB 'RD' /* not used, so use it as password enhancer */ ORG ADC10_VECTOR /* 0xFFEA ADC10 */ DW ADC10_JMP ORG USCIAB0TX_VECTOR /* 0xFFEC USCI A0/B0 Transmit */ DW USCIAB0TX_JMP ORG USCIAB0RX_VECTOR /* 0xFFEE USCI A0/B0 Receive */ DW USCIAB0RX_JMP ORG TIMER0_A1_VECTOR /* 0xFFF0 Timer0)A CC1, TA0 */ DW TIMER0_A1_JMP ORG TIMER0_A0_VECTOR /* 0xFFF2 Timer0_A CC0 */ DW TIMER0_A0_JMP ORG WDT_VECTOR /* 0xFFF4 Watchdog Timer */ DW WDT_JMP ORG COMPARATORA_VECTOR /* 0xFFF6 Comparator A */ DW COMPARATORA_JMP ORG TIMER1_A1_VECTOR /* 0xFFF8 Timer1_A CC1-4, TA1 */ DW TIMER1_A1_JMP ORG TIMER1_A0_VECTOR /* 0xFFFA Timer1_A CC0 */ DW TIMER1_A0_JMP ORG NMI_VECTOR /* 0xFFFC Non-maskable */ DW NMI_JMP ORG RESET_VECTOR /* 0xFFFE Reset [Highest Priority] */ DW RESET_JMP END
