mirror of
https://github.com/emmansun/gmsm.git
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53 lines
1.4 KiB
Go
53 lines
1.4 KiB
Go
package zuc
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import (
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"crypto/cipher"
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"encoding/binary"
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"github.com/emmansun/gmsm/internal/alias"
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"github.com/emmansun/gmsm/internal/subtle"
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)
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const RoundWords = 32
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// NewCipher create a stream cipher based on key and iv aguments.
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func NewCipher(key, iv []byte) (cipher.Stream, error) {
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return newZUCState(key, iv)
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}
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// NewEEACipher create a stream cipher based on key, count, bearer and direction arguments according specification.
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func NewEEACipher(key []byte, count, bearer, direction uint32) (cipher.Stream, error) {
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iv := make([]byte, 16)
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binary.BigEndian.PutUint32(iv, count)
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copy(iv[8:12], iv[:4])
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iv[4] = byte(((bearer << 1) | (direction & 1)) << 2)
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iv[12] = iv[4]
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return newZUCState(key, iv)
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}
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func xorKeyStreamGeneric(c *zucState32, dst, src []byte) {
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words := (len(src) + 3) / 4
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rounds := words / RoundWords
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var keyBytes [RoundWords * 4]byte
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for i := 0; i < rounds; i++ {
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genKeyStreamRev32(keyBytes[:], c)
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subtle.XORBytes(dst, src, keyBytes[:])
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dst = dst[RoundWords*4:]
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src = src[RoundWords*4:]
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}
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if rounds*RoundWords < words {
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genKeyStreamRev32(keyBytes[:4*(words-rounds*RoundWords)], c)
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subtle.XORBytes(dst, src, keyBytes[:])
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}
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}
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func (c *zucState32) XORKeyStream(dst, src []byte) {
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if len(dst) < len(src) {
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panic("zuc: output smaller than input")
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}
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if alias.InexactOverlap(dst[:len(src)], src) {
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panic("zuc: invalid buffer overlap")
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}
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xorKeyStream(c, dst, src)
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}
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