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tea.go
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tea.go
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// https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm
package main
import (
"encoding/binary"
"flag"
"fmt"
"log"
"os"
)
var (
endian = flag.String("i", "little", "specify endian order")
openc = flag.Bool("e", false, "encrypt input")
opdec = flag.Bool("d", false, "decrypt input")
)
func main() {
log.SetPrefix("tea: ")
log.SetFlags(0)
flag.Usage = usage
flag.Parse()
if flag.NArg() != 3 {
usage()
}
var order binary.ByteOrder
if *endian == "little" {
order = binary.LittleEndian
} else {
order = binary.BigEndian
}
key := convert([]byte(flag.Arg(0)), order)
if len(key) != 4 {
log.Fatal("invalid key length")
}
buf, err := os.ReadFile(flag.Arg(1))
ck(err)
data := convert(buf, order)
var out32 []uint32
if *openc {
out32 = docrypt(key, data, 'e')
} else if *opdec {
out32 = docrypt(key, data, 'd')
} else {
usage()
}
out := deconvert(out32)
ck(os.WriteFile(flag.Arg(2), out, 0644))
}
func ck(err error) {
if err != nil {
log.Fatal(err)
}
}
func usage() {
fmt.Fprintln(os.Stderr, "usage: key infile outfile")
flag.PrintDefaults()
os.Exit(2)
}
func docrypt(key, data []uint32, op int) []uint32 {
var p []uint32
for i := 0; i < len(data); i += 2 {
var v [2]uint32
v[0] = data[0]
v[1] = data[1]
if op == 'e' {
encrypt(v[:], key)
} else {
decrypt(v[:], key)
}
p = append(p, v[:]...)
}
return p
}
func deconvert(b []uint32) []byte {
var p []byte
var o [4]byte
for i := range b {
binary.LittleEndian.PutUint32(o[:], b[i])
p = append(p, o[:]...)
}
return p
}
func convert(b []byte, e binary.ByteOrder) []uint32 {
var p []uint32
for i := 0; i < len(b)/4; i++ {
p = append(p, e.Uint32(b[4*i:]))
}
n := len(b) % 4
if n != 0 {
var m [4]byte
copy(m[:], b[:len(b)-n])
p = append(p, e.Uint32(m[:]))
}
if len(p)%2 != 0 {
p = append(p, 0)
}
return p
}
func encrypt(v, k []uint32) {
v0 := v[0]
v1 := v[1]
sum := uint32(0)
delta := uint32(0x9e3779b9)
k0 := k[0]
k1 := k[1]
k2 := k[2]
k3 := k[3]
for i := 0; i < 32; i++ {
sum += delta
v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1)
v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3)
}
v[0] = v0
v[1] = v1
}
func decrypt(v, k []uint32) {
v0 := v[0]
v1 := v[1]
sum := uint32(0xC6EF3720)
delta := uint32(0x9e3779b9)
k0 := k[0]
k1 := k[1]
k2 := k[2]
k3 := k[3]
for i := 0; i < 32; i++ {
v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3)
v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1)
sum -= delta
}
v[0] = v0
v[1] = v1
}