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forked from um/cli
cli/algo/ximalaya/x3m_crypto.go

41 lines
957 B
Go
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2022-11-19 23:53:36 +00:00
package ximalaya
import (
_ "embed"
"encoding/binary"
)
var x3mKey = [...]byte{
'3', '9', '8', '9', 'd', '1', '1', '1',
'a', 'a', 'd', '5', '6', '1', '3', '9',
'4', '0', 'f', '4', 'f', 'c', '4', '4',
'b', '6', '3', '9', 'b', '2', '9', '2',
}
const x3mHeaderSize = 1024
var x3mScrambleTable = [x3mHeaderSize]uint16{}
//go:embed x3m_scramble_table.bin
var x3mScrambleTableBytes []byte
func init() {
if len(x3mScrambleTableBytes) != 2*x3mHeaderSize {
panic("invalid x3m scramble table")
}
for i := range x3mScrambleTable {
x3mScrambleTable[i] = binary.LittleEndian.Uint16(x3mScrambleTableBytes[i*2:])
}
}
// decryptX3MHeader decrypts the header of ximalaya .x3m file.
// make sure input src is 1024 (x3mHeaderSize) bytes long.
func decryptX3MHeader(src []byte) []byte {
dst := make([]byte, len(src))
for dstIdx := range src {
srcIdx := x3mScrambleTable[dstIdx]
dst[dstIdx] = src[srcIdx] ^ x3mKey[dstIdx%len(x3mKey)]
}
return dst
}