ceremonyclient/nekryptology/pkg/ot/base/simplest/util.go

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2023-07-05 05:32:28 +00:00
package simplest
import (
"io"
)
// xorBytes computes c = a xor b.
func xorBytes(a, b [DigestSize]byte) (c [DigestSize]byte) {
for i := 0; i < DigestSize; i++ {
c[i] = a[i] ^ b[i]
}
return
}
// initChoice initializes the receiver's choice array from the PackedRandomChoiceBits array
func (receiver *Receiver) initChoice() {
// unpack the random values in PackedRandomChoiceBits into bits in Choice
receiver.Output.RandomChoiceBits = make([]int, receiver.batchSize)
for i := 0; i < len(receiver.Output.RandomChoiceBits); i++ {
receiver.Output.RandomChoiceBits[i] = int(ExtractBitFromByteVector(receiver.Output.PackedRandomChoiceBits, i))
}
}
// ExtractBitFromByteVector interprets the byte-vector `vector` as if it were a _bit_-vector with len(vector) * 8 bits.
// it extracts the `index`th such bit, interpreted in the little-endian way (i.e., both across bytes and within bytes).
func ExtractBitFromByteVector(vector []byte, index int) byte {
// the bitwise tricks index >> 3 == index // 8 and index & 0x07 == index % 8 are designed to avoid CPU division.
return vector[index>>3] >> (index & 0x07) & 0x01
}
type pipeWrapper struct {
r *io.PipeReader
w *io.PipeWriter
exchanged int // used this during testing, to track bytes exchanged
}
func (wrapper *pipeWrapper) Write(p []byte) (n int, err error) {
n, err = wrapper.w.Write(p)
wrapper.exchanged += n
return
}
func (wrapper *pipeWrapper) Read(p []byte) (n int, err error) {
n, err = wrapper.r.Read(p)
wrapper.exchanged += n
return
}
func NewPipeWrappers() (*pipeWrapper, *pipeWrapper) {
leftOut, leftIn := io.Pipe()
rightOut, rightIn := io.Pipe()
return &pipeWrapper{r: leftOut, w: rightIn}, &pipeWrapper{r: rightOut, w: leftIn}
}