encoding

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 Go to latest Published: Jan 12, 2022 License: BSD-3-Clause Imports: 7 Imported by: 0

Documentation

Overview

Package encoding defines interfaces to be implemented by bijective, invertible functions. Implementing a common interface over the building blocks of a construction or cryptanalysis gives a simple way to compose, concatenate, and invert them.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func EquivalentBytes 

func EquivalentBytes(a, b Byte) bool

EquivalentBytes returns true if two Byte encodings are identical and false if not.

func ProbablyEquivalentBlocks 

func ProbablyEquivalentBlocks(a, b Block) bool

ProbablyEquivalentBlocks returns true if two Block encodings are probably equivalent and false if they're definitely not.

func ProbablyEquivalentDoubles 

func ProbablyEquivalentDoubles(a, b Double) bool

ProbablyEquivalentDoubles returns true if two Double encodings are probably equivalent and false if they're definitely not.

func ProbablyEquivalentWords 

func ProbablyEquivalentWords(a, b Word) bool

ProbablyEquivalentWords returns true if two Word encodings are probably equivalent and false if they're definitely not.

func SerializeByte 

func SerializeByte(e Byte) []byte

SerializeByte serializes a Byte encoding to a byte slice.

func XOR 

func XOR(dst, a, b []byte) int

XOR xors the bytes in a and b. The destination is assumed to have enough space. Returns the number of bytes xor'd.

Types

type Block 

type Block interface {
	Encode(i [16]byte) [16]byte
	Decode(i [16]byte) [16]byte
}

type BlockAdditive 

type BlockAdditive [16]byte

BlockAdditive implements the Block interface over XORing with a fixed value.

func (BlockAdditive) Decode 

func (ba BlockAdditive) Decode(in [16]byte) [16]byte

func (BlockAdditive) Encode 

func (ba BlockAdditive) Encode(in [16]byte) [16]byte

type BlockAffine 

type BlockAffine struct {
	BlockLinear
	BlockAdditive
}

BlockAffine implements the Block interface over an affine transformation (a linear transformation composed with an additive one).

func DecomposeBlockAffine 

func DecomposeBlockAffine(in Block) (BlockAffine, bool)

DecomposeBlockAffine decomposes an opaque Block encoding into a BlockAffine encoding.

func NewBlockAffine 

func NewBlockAffine(forwards matrix.Matrix, constant [16]byte) BlockAffine

NewBlockAffine constructs a new BlockAffine encoding from a matrix and a constant.

func (BlockAffine) Decode 

func (ba BlockAffine) Decode(in [16]byte) [16]byte

func (BlockAffine) Encode 

func (ba BlockAffine) Encode(in [16]byte) [16]byte

type BlockLinear 

type BlockLinear struct {
	// Forwards is the matrix to multiply by in the forwards (encoding) direction.
	Forwards matrix.Matrix
	// Backwards is the matrix to multiply by in the backwards (decoding) direction. It should be the inverse of Forwards.
	Backwards matrix.Matrix
}

BlockLinear implements the Block interface over a 128x128 linear transformation.

func DecomposeBlockLinear 

func DecomposeBlockLinear(in Block) (BlockLinear, bool)

DecomposeBlockLinear decomposes an opaque Block encoding into a BlockLinear encoding.

func NewBlockLinear 

func NewBlockLinear(forwards matrix.Matrix) BlockLinear

NewBlockLinear constructs a new BlockLinear encoding from a given matrix.

func (BlockLinear) Decode 

func (bl BlockLinear) Decode(in [16]byte) (out [16]byte)

func (BlockLinear) Encode 

func (bl BlockLinear) Encode(in [16]byte) (out [16]byte)

type BlockTable 

type BlockTable struct {
	In     Byte
	Out    Block
	Hidden table.Block
}

BlockTable implements the table.Block interface over another Block table with a Byte encoding on its input and a Block encoding on its output.

func (BlockTable) Get 

func (bt BlockTable) Get(i byte) [16]byte

type Byte 

type Byte interface {
	Encode(i byte) byte
	Decode(i byte) byte
}

func ParseByte 

func ParseByte(serialized []byte) Byte

ParseByte parses a serialized Byte encoding.

type ByteAdditive 

type ByteAdditive byte

ByteAdditive implements the Byte interface over XORing with a fixed value.

func (ByteAdditive) Decode 

func (ba ByteAdditive) Decode(in byte) byte

func (ByteAdditive) Encode 

func (ba ByteAdditive) Encode(in byte) byte

type ByteAffine 

type ByteAffine struct {
	ByteLinear
	ByteAdditive
}

ByteAffine implements the Byte interface over an affine transformation (a linear transformation composed with an additive one).

func DecomposeByteAffine 

func DecomposeByteAffine(in Byte) (ByteAffine, bool)

DecomposeByteAffine decomposes an opaque Byte encoding into a ByteAffine encoding.

func NewByteAffine 

func NewByteAffine(forwards matrix.Matrix, constant byte) ByteAffine

NewByteAffine constructs a new ByteAffine encoding from a matrix and a constant.

func (ByteAffine) Decode 

func (ba ByteAffine) Decode(in byte) byte

func (ByteAffine) Encode 

func (ba ByteAffine) Encode(in byte) byte

type ByteLinear 

type ByteLinear struct {
	// Forwards is the matrix to multiply by in the forwards (encoding) direction.
	Forwards matrix.Matrix
	// Backwards is the matrix to multiply by in the backwards (decoding) direction. It should be the inverse of Forwards.
	Backwards matrix.Matrix
}

ByteLinear implements the Byte interface over an 8x8 linear transformation.

func DecomposeByteLinear 

func DecomposeByteLinear(in Byte) (ByteLinear, bool)

DecomposeByteLinear decomposes an opaque Byte encoding into a ByteLinear encoding.

func NewByteLinear 

func NewByteLinear(forwards matrix.Matrix) ByteLinear

NewByteLinear constructs a new ByteLinear encoding from a given matrix.

func (ByteLinear) Decode 

func (bl ByteLinear) Decode(in byte) byte

func (ByteLinear) Encode 

func (bl ByteLinear) Encode(in byte) byte

type ByteMultiplication 

type ByteMultiplication struct {
	// Forwards is the number to multiply by in the forwards (encoding) direction.
	Forwards number.ByteFieldElem
	// Backwards is the number to multiply by in the backwards (decoding) direction. It should be the inverse of Forwards.
	Backwards number.ByteFieldElem
}

ByteMultiplication implements the Byte interface over multiplication by an element of GF(2^8).

func NewByteMultiplication 

func NewByteMultiplication(forwards number.ByteFieldElem) ByteMultiplication

NewByteMultiplication constructs a new ByteMultiplication encoding from a field element.

func (ByteMultiplication) Decode 

func (bm ByteMultiplication) Decode(i byte) byte

func (ByteMultiplication) Encode 

func (bm ByteMultiplication) Encode(i byte) byte

type ByteTable 

type ByteTable struct {
	In     Byte
	Out    Byte
	Hidden table.Byte
}

ByteTable implements the table.Byte interface over another Byte table with Byte encodings on its input and output.

func (ByteTable) Get 

func (bt ByteTable) Get(i byte) byte

type ComposedBlocks 

type ComposedBlocks []Block

ComposedBlocks converts an array of Block encodings into one by chaining them. See ComposedBytes.

func (ComposedBlocks) Decode 

func (cb ComposedBlocks) Decode(i [16]byte) (out [16]byte)

func (ComposedBlocks) Encode 

func (cb ComposedBlocks) Encode(i [16]byte) (out [16]byte)

type ComposedBytes 

type ComposedBytes []Byte

ComposedBytes converts an array of Byte encodings into one by chaining them. Functions are chained in REVERSE order than they would be in function composition notation.

Example: 

f := ComposedBytes([]Byte{A, B, C}) // f(x) = C(B(A(x)))

func (ComposedBytes) Decode 

func (cb ComposedBytes) Decode(i byte) byte

func (ComposedBytes) Encode 

func (cb ComposedBytes) Encode(i byte) byte

type ComposedDoubles 

type ComposedDoubles []Double

ComposedDoubles converts an array of Double encodings into one by chaining them. See ComposedBytes.

func (ComposedDoubles) Decode 

func (cd ComposedDoubles) Decode(i [2]byte) (out [2]byte)

func (ComposedDoubles) Encode 

func (cd ComposedDoubles) Encode(i [2]byte) (out [2]byte)

type ComposedWords 

type ComposedWords []Word

ComposedWords converts an array of Word encodings into one by chaining them. See ComposedBytes.

func (ComposedWords) Decode 

func (cw ComposedWords) Decode(i [4]byte) (out [4]byte)

func (ComposedWords) Encode 

func (cw ComposedWords) Encode(i [4]byte) (out [4]byte)

type ConcatenatedBlock 

type ConcatenatedBlock [16]Byte

ConcatenatedBlock builds a Block encoding by concatenating sixteen Byte encodings. The Byte encoding in position i is the one applied to position i of the input.

func DecomposeConcatenatedBlock 

func DecomposeConcatenatedBlock(in Block) (out ConcatenatedBlock)

DecomposeConcatenatedBlock decomposes an opaque concatenated Block encoding into an explicit one.

func (ConcatenatedBlock) Decode 

func (cb ConcatenatedBlock) Decode(i [16]byte) (out [16]byte)

func (ConcatenatedBlock) Encode 

func (cb ConcatenatedBlock) Encode(i [16]byte) (out [16]byte)

type ConcatenatedByte 

type ConcatenatedByte [2]Nibble

ConcatenatedByte builds a Byte encoding by concatenating two Nibble encodings. The Nibble encoding in position 0 is applied to the upper half of the byte and the one in position 1 is applied to the lower half.

func (ConcatenatedByte) Decode 

func (cb ConcatenatedByte) Decode(i byte) byte

func (ConcatenatedByte) Encode 

func (cb ConcatenatedByte) Encode(i byte) byte

type ConcatenatedDouble 

type ConcatenatedDouble [2]Byte

ConcatenatedDouble builds a Double encoding by Concatenating two Byte encodings. The Byte encoding in position i is the one applied to position i of the input.

func (ConcatenatedDouble) Decode 

func (cd ConcatenatedDouble) Decode(i [2]byte) [2]byte

func (ConcatenatedDouble) Encode 

func (cd ConcatenatedDouble) Encode(i [2]byte) [2]byte

type ConcatenatedWord 

type ConcatenatedWord [4]Byte

ConcatenatedWord builds a Word encoding by concatenating four Byte encodings. The Byte encoding in position i is the one applied to position i of the input.

func (ConcatenatedWord) Decode 

func (cw ConcatenatedWord) Decode(i [4]byte) [4]byte

func (ConcatenatedWord) Encode 

func (cw ConcatenatedWord) Encode(i [4]byte) [4]byte

type Double 

type Double interface {
	Encode(i [2]byte) [2]byte
	Decode(i [2]byte) [2]byte
}

type DoubleAdditive 

type DoubleAdditive [2]byte

DoubleAdditive implements the Double interface over XORing with a fixed value.

func (DoubleAdditive) Decode 

func (da DoubleAdditive) Decode(in [2]byte) [2]byte

func (DoubleAdditive) Encode 

func (da DoubleAdditive) Encode(in [2]byte) [2]byte

type DoubleAffine 

type DoubleAffine struct {
	DoubleLinear
	DoubleAdditive
}

DoubleAffine implements the Double interface over an affine transformation (a linear transformation composed with an additive one).

func DecomposeDoubleAffine 

func DecomposeDoubleAffine(in Double) (DoubleAffine, bool)

DecomposeDoubleAffine decomposes an opaque Double encoding into a DoubleAffine encoding.

func NewDoubleAffine 

func NewDoubleAffine(forwards matrix.Matrix, constant [2]byte) DoubleAffine

NewDoubleAffine constructs a new DoubleAffine encoding from a matrix and a constant.

func (DoubleAffine) Decode 

func (da DoubleAffine) Decode(in [2]byte) [2]byte

func (DoubleAffine) Encode 

func (da DoubleAffine) Encode(in [2]byte) [2]byte

type DoubleLinear 

type DoubleLinear struct {
	// Forwards is the matrix to multiply by in the forwards (encoding) direction.
	Forwards matrix.Matrix
	// Backwards is the matrix to multiply by in the backwards (decoding) direction. It should be the inverse of Forwards.
	Backwards matrix.Matrix
}

DoubleLinear implements the Double interface over a 16x16 linear transformation.

func DecomposeDoubleLinear 

func DecomposeDoubleLinear(in Double) (DoubleLinear, bool)

DecomposeDoubleLinear decomposes an opaque Double encoding into a DoubleLinear encoding.

func NewDoubleLinear 

func NewDoubleLinear(forwards matrix.Matrix) DoubleLinear

NewDoubleLinear constructs a new DoubleLinear encoding from a given matrix.

func (DoubleLinear) Decode 

func (dl DoubleLinear) Decode(in [2]byte) (out [2]byte)

func (DoubleLinear) Encode 

func (dl DoubleLinear) Encode(in [2]byte) (out [2]byte)

type DoubleToByteTable 

type DoubleToByteTable struct {
	In     Double
	Out    Byte
	Hidden table.DoubleToByte
}

DoubleToByteTable implements the table.DoubleToByte interface over another DoubleToByte table with a Double encoding on its input and a Byte encoding on its output.

func (DoubleToByteTable) Get 

func (dtbt DoubleToByteTable) Get(i [2]byte) byte

type DoubleToWordTable 

type DoubleToWordTable struct {
	In     Double
	Out    Word
	Hidden table.DoubleToWord
}

DoubleToWordTable implements the table.DoubleToWord interface over another DoubleToWord table with a Double encoding on its input and a Word encoding on its output.

func (DoubleToWordTable) Get 

func (dtwt DoubleToWordTable) Get(i [2]byte) [4]byte

type IdentityBlock 

type IdentityBlock struct{}

IdentityBlock is the identity operation on blocks.

func (IdentityBlock) Decode 

func (ib IdentityBlock) Decode(i [16]byte) (out [16]byte)

func (IdentityBlock) Encode 

func (ib IdentityBlock) Encode(i [16]byte) (out [16]byte)

type IdentityByte 

type IdentityByte struct{}

IdentityByte is the identity operation on bytes. It is used in place of an IdentityNibble encoding.

func (IdentityByte) Decode 

func (ib IdentityByte) Decode(i byte) byte

func (IdentityByte) Encode 

func (ib IdentityByte) Encode(i byte) byte

type IdentityDouble 

type IdentityDouble struct{}

IdentityDouble is the identity operation on doubles.

func (IdentityDouble) Decode 

func (id IdentityDouble) Decode(i [2]byte) [2]byte

func (IdentityDouble) Encode 

func (id IdentityDouble) Encode(i [2]byte) [2]byte

type IdentityWord 

type IdentityWord struct{}

IdentityWord is the identity operation on words.

func (IdentityWord) Decode 

func (iw IdentityWord) Decode(i [4]byte) (out [4]byte)

func (IdentityWord) Encode 

func (iw IdentityWord) Encode(i [4]byte) (out [4]byte)

type InverseBlock 

type InverseBlock struct{ Block }

InverseBlock swaps the Encode and Decode methods of a Block encoding.

func (InverseBlock) Decode 

func (ib InverseBlock) Decode(i [16]byte) [16]byte

func (InverseBlock) Encode 

func (ib InverseBlock) Encode(i [16]byte) [16]byte

type InverseByte 

type InverseByte struct{ Byte }

InverseByte swaps the Encode and Decode methods of a Byte encoding.

func (InverseByte) Decode 

func (ib InverseByte) Decode(i byte) byte

func (InverseByte) Encode 

func (ib InverseByte) Encode(i byte) byte

type InverseDouble 

type InverseDouble struct{ Double }

InverseDouble swaps the Encode and Decode methods of a Double encoding.

func (InverseDouble) Decode 

func (id InverseDouble) Decode(i [2]byte) [2]byte

func (InverseDouble) Encode 

func (id InverseDouble) Encode(i [2]byte) [2]byte

type InverseWord 

type InverseWord struct{ Word }

InverseWord swaps the Encode and Decode methods of a Word encoding.

func (InverseWord) Decode 

func (iw InverseWord) Decode(i [4]byte) [4]byte

func (InverseWord) Encode 

func (iw InverseWord) Encode(i [4]byte) [4]byte

type Nibble 

type Nibble interface {
	Encode(i byte) byte // Encode(i nibble) nibble
	Decode(i byte) byte // Decode(i nibble) nibble
}

Nibble is the same interface as Byte. A function implementing Nibble shouldn't accept inputs or give outputs over 16.

type NibbleTable 

type NibbleTable struct {
	In     Byte
	Out    Nibble
	Hidden table.Nibble
}

NibbleTable implements the table.Nibble interface over another Nibble table with a Byte encoding on its input and a Nibble encoding on its output.

func (NibbleTable) Get 

func (nt NibbleTable) Get(i byte) byte

type SBox 

type SBox struct {
	EncKey, DecKey [256]byte
}

SBox implements a random 8-bit bijection.

func GenerateSBox 

func GenerateSBox(reader io.Reader) (s SBox)

GenerateSBox generates a random 8-bit bijection using the random source random (for example, crypto/rand.Reader).

func (SBox) Decode 

func (s SBox) Decode(i byte) byte

func (SBox) Encode 

func (s SBox) Encode(i byte) byte

func (SBox) Permutation 

func (s SBox) Permutation() (out []int)

Permutation returns the SBox's permutation.

type Shuffle 

type Shuffle struct {
	EncKey, DecKey [16]byte
}

Shuffle implements a random 4-bit bijection.

func GenerateShuffle 

func GenerateShuffle(reader io.Reader) (s Shuffle)

GenerateShuffle generates a random 4-bit bijection using the random source random (for example, crypto/rand.Reader).

func (Shuffle) Decode 

func (s Shuffle) Decode(i byte) byte

func (Shuffle) Encode 

func (s Shuffle) Encode(i byte) byte

func (Shuffle) Permutation 

func (s Shuffle) Permutation() (out []int)

Permutation returns the shuffle's permutation.

type Word 

type Word interface {
	Encode(i [4]byte) [4]byte
	Decode(i [4]byte) [4]byte
}

type WordAdditive 

type WordAdditive [4]byte

WordAdditive implements the Word interface over XORing with a fixed value.

func (WordAdditive) Decode 

func (wa WordAdditive) Decode(in [4]byte) [4]byte

func (WordAdditive) Encode 

func (wa WordAdditive) Encode(in [4]byte) [4]byte

type WordAffine 

type WordAffine struct {
	WordLinear
	WordAdditive
}

WordAffine implements the Word interface over an affine transformation (a linear transformation composed with an additive one).

func DecomposeWordAffine 

func DecomposeWordAffine(in Word) (WordAffine, bool)

DecomposeWordAffine decomposes an opaque Word encoding into a WordAffine encoding.

func NewWordAffine 

func NewWordAffine(forwards matrix.Matrix, constant [4]byte) WordAffine

NewWordAffine constructs a new WordAffine encoding from a matrix and a constant.

func (WordAffine) Decode 

func (wa WordAffine) Decode(in [4]byte) [4]byte

func (WordAffine) Encode 

func (wa WordAffine) Encode(in [4]byte) [4]byte

type WordLinear 

type WordLinear struct {
	// Forwards is the matrix to multiply by in the forwards (encoding) direction.
	Forwards matrix.Matrix
	// Backwards is the matrix to multiply by in the backwards (decoding) direction. It should be the inverse of Forwards.
	Backwards matrix.Matrix
}

WordLinear implements the Word interface over a 32x32 linear transformation.

func DecomposeWordLinear 

func DecomposeWordLinear(in Word) (WordLinear, bool)

DecomposeWordLinear decomposes an opaque Word encoding into a WordLinear encoding.

func NewWordLinear 

func NewWordLinear(forwards matrix.Matrix) WordLinear

NewWordLinear constructs a new WordLinear encoding from a given matrix.

func (WordLinear) Decode 

func (wl WordLinear) Decode(in [4]byte) (out [4]byte)

func (WordLinear) Encode 

func (wl WordLinear) Encode(in [4]byte) (out [4]byte)

type WordTable 

type WordTable struct {
	In     Byte
	Out    Word
	Hidden table.Word
}

WordTable implements the table.Word interface over another Word table with a Byte encoding on its input and a Word encoding on its output.

func (WordTable) Get 

func (wt WordTable) Get(i byte) [4]byte

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