# 83Plus:BCALLs:80C0

From WikiTI

## Synopsis

**Official Name:** bignumpowermod17

**BCALL Address:** 80C0

Raises a big integer to the 17th power.

### Inputs

### Outputs

### Destroys

- All registers
- 8100h: 130-byte area which the multiplication routine uses to store its result
- 8182h: 65-byte area used as the first argument to the multiplication routine
- 81C3h: 65-byte area used as the second argument to the multiplication routine

## Comments

This BCALL takes a large integer pointed at address 8182h and raises it to the 17th power (modulo the current public key.) The OS uses this to decrypt RSA signatures, such as those used for certificate blocks. This differs only from RSAValidate in that this romcall expects the signature to already be copied to 8182h.