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