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Routines |
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Runs "RRD" on each of the 31744 bytes that start at 24575 which decrypts the game, and then jumps to SecurityCheck.
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Set up the address of the first byte to decrypt and the counters.
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| GameEntry | 23424 | LD HL,24575 | HL=24575 (the address of the first byte to decrypt). | |
| 23427 | LD BC,124 | BC=0124 (B=0 so the inner loop runs 256 times, and C counts the 124 outer passes). | ||
| 23430 | XOR A | A=0 (and reset the flags). | ||
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Rotate the nibbles of each byte, chaining the low nibble of one byte into the high nibble of the next.
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| Decryption_Loop | 23431 | RRD | RRD operation on *HL. | |
| 23433 | INC HL | Move HL on to the next byte to decrypt. | ||
| 23434 | DJNZ Decryption_Loop | Decrease the byte counter (B) by one and loop back to Decryption_Loop until all 256 bytes have been done. | ||
| 23436 | DEC C | Decrease the pass counter (C) by one and loop back to Decryption_Loop until all 124 passes have been done. | ||
| 23437 | JR NZ,Decryption_Loop | |||
| 23439 | JP SecurityCheck | Jump to SecurityCheck to run the security check. | ||
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View the equivalent code in Lunar Jetman.
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