crypto.go

package main

import (
	"crypto/rsa"
	"math/big"
)

var (
	publicKey = rsa.PublicKey{
		E: 0x10001,
		N: new(big.Int).SetBytes([]byte{
			0x51, 0xbc, 0xda, 0x08, 0x6d, 0x39, 0xfc, 0xe4,
			0x56, 0x51, 0x60, 0xd6, 0x51, 0x71, 0x3f, 0xa2,
			0xe8, 0xaa, 0x54, 0xfa, 0x66, 0x82, 0xb0, 0x4a,
			0xab, 0xdd, 0x0e, 0x6a, 0xf8, 0xb0, 0xc1, 0xe6,
			0xd1, 0xfb, 0x4f, 0x3d, 0xaa, 0x43, 0x7f, 0x15,
		}),
	}

	privateKey = rsa.PrivateKey{
		PublicKey: publicKey,
		D: new(big.Int).SetBytes([]byte{
			0x0a, 0x56, 0x37, 0xbc, 0x99, 0x13, 0x9c, 0x47,
			0xc4, 0x22, 0xc6, 0x7c, 0x54, 0x10, 0x5e, 0x5b,
			0xdb, 0xd0, 0xae, 0xae, 0x4a, 0xb4, 0xd4, 0x33,
			0x43, 0x58, 0x27, 0x4e, 0x1b, 0xdf, 0x57, 0x06,
			0xa1, 0xfb, 0xf4, 0xe6, 0x82, 0x89, 0x30, 0x81,
		}),
		Primes: []*big.Int{
			new(big.Int).SetBytes([]byte{
				0x01, 0x45, 0xd2, 0x58, 0x2f, 0x15, 0x95, 0x27,
				0x04, 0xba, 0x91, 0x87, 0x8c, 0x88, 0xe4, 0x86,
				0x46, 0x4d, 0x67, 0x75, 0x3f,
			}),
			new(big.Int).SetBytes([]byte{
				0x40, 0x38, 0xc7, 0x8c, 0x87, 0x1a, 0x1b, 0x97,
				0x90, 0xbb, 0xcd, 0x71, 0x3c, 0x28, 0xdb, 0xab,
				0x84, 0xe6, 0x52, 0xab,
			}),
		},
	}
)

// RSA transform function.
// To encrypt: rsatransform(block, E, N)
// To decrypt: rsatransform(block, D, N)
func rsatransform(block []byte, y, m *big.Int) []byte {
	x := new(big.Int).SetBytes(block)
	return new(big.Int).Exp(x, y, m).Bytes()
}

func blowfishKeyFromKeySource(keySource []byte) []byte {
	ks := [80]byte{}
	copy(ks[:], keySource)
	byteswap(ks[:])
	E := big.NewInt(int64(publicKey.E))
	s0 := rsatransform(ks[:40], E, publicKey.N)
	s1 := rsatransform(ks[40:], E, publicKey.N)
	a := new(big.Int).SetBytes(s0)
	b := new(big.Int).SetBytes(s1)
	c := new(big.Int).Lsh(a, 312)
	d := new(big.Int).Add(b, c)
	key := d.Bytes()
	byteswap(key)
	return key
}