32 lines
607 B
Go
32 lines
607 B
Go
package kwm
|
|
|
|
import (
|
|
"encoding/binary"
|
|
"strconv"
|
|
)
|
|
|
|
type kwmCipher struct {
|
|
mask []byte
|
|
}
|
|
|
|
func newKwmCipher(key []byte) *kwmCipher {
|
|
return &kwmCipher{mask: generateMask(key)}
|
|
}
|
|
|
|
func generateMask(key []byte) []byte {
|
|
keyInt := binary.LittleEndian.Uint64(key)
|
|
keyStr := strconv.FormatUint(keyInt, 10)
|
|
keyStrTrim := padOrTruncate(keyStr, 32)
|
|
mask := make([]byte, 32)
|
|
for i := 0; i < 32; i++ {
|
|
mask[i] = keyPreDefined[i] ^ keyStrTrim[i]
|
|
}
|
|
return mask
|
|
}
|
|
|
|
func (c kwmCipher) Decrypt(buf []byte, offset int) {
|
|
for i := range buf {
|
|
buf[i] ^= c.mask[(offset+i)&0x1F] // equivalent: [i % 32]
|
|
}
|
|
}
|