Masking Class Reference

Masking class that provides functionality for masking and unmasking AES-decryption. More...

#include <masking.h>

Collaboration diagram for Masking:

Classes
struct	mask_t
	Structure for masks. Masks always come in pairs, with an input & output mask. More...

Public Member Functions
	Masking ()=default
	Construct a new Masking object.
void	init ()
	Initialize the masks & the masked inverse S-Box. More...
void	maskSubKeys (const sub_keys_t subKeys, sub_keys_t maskedSubKeys) const
	Mask the subKeys & store the masked keys in maskedSubKeys. More...
void	invMaskState (state_t state) const
	(Inverse) mask the state before the first AddRoundKey step. More...
void	invReMaskState (state_t state) const
	(Inverse) re-mask the state after every MixCol step. More...
void	invUnMaskState (state_t state) const
	(Inverse) un-mask the state after the last AddRoundKey step. More...
uint8_t	getInvMaskedSBoxValue (const uint8_t index) const
	Get a value of the (inverse) masked S-Box at a specific index. More...

Private Member Functions
void	initInvMaskedSBox (uint8_t maskedSBox[], const mask_t &subByteMask) const
	Compute the (inverse) masked S-Box. More...
void	initMixColInputMask (mask_t mixColMasks[]) const
	Compute masks m_i, i=1..4, by performing a MixCol operation on masks m_i'. More...

Private Attributes
uint8_t	mInvMaskedSBox [SBOX_BYTES]
	Inverse S-Box with masked values.
mask_t	mSubByteMask = {}
	SubByte input & output mask. More...
mask_t	mMixColMasks [4] = {}
	4 MixCol input & output masks. More...
RNG	mRNG
	Random-Number-Generator.
Logger	mLog
	Logger.

Detailed Description

Masking class that provides functionality for masking and unmasking AES-decryption.

The masking techniques used here are strongly based on the work presented by Mangard, Oswald & Popp in their book "Power Analysis Attacks: Revealing the Secrets of Smart Cards". The implementation presented on pp. 228 ff. for encryption was adjusted to fit the decryption that was implemented here.

Authors

Philipp Karg (phili.nosp@m.pp.k.nosp@m.arg@t.nosp@m.um.d.nosp@m.e)

Date

28.06.2022

Copyright

Philipp Karg 2022

Member Function Documentation

getInvMaskedSBoxValue()

uint8_t Masking::getInvMaskedSBoxValue ( const uint8_t  index ) const

inline

Get a value of the (inverse) masked S-Box at a specific index.

Parameters

[in]

index

(const uint8_t): Index to get value for.

Returns

(uint8_t): The value at index.

init()

void Masking::init

(

)

Initialize the masks & the masked inverse S-Box.

1. Seed the Random-Number-Generator.
2. Create random m & m' masks.
3. Create the masked inverse S-Box, by calling initInvMaskedSBox().
4. Create random masks m_i', i=1..4.
5. Calculate the corresponding masks m_i, i=1..4 by calling initMixColInputMask().

initInvMaskedSBox()

void Masking::initInvMaskedSBox ( uint8_t  maskedSBox[], const mask_t &  subByteMask  ) const

private

Compute the (inverse) masked S-Box.

Masking is done as follows: S_masked(x + m') = S(x) + m, where x is any index of the S-Box.

See also

"Power Analysis Attacks" by Mangard et. al. p. 228 ff.

Parameters

[out]	maskedSBox	(uint8_t*): The masked S-Box.
[in]	subByteMask	(const mask_t): Masks m & m'.

initMixColInputMask()

void Masking::initMixColInputMask ( mask_t  mixColMasks[] ) const

private

Compute masks m_i, i=1..4, by performing a MixCol operation on masks m_i'.

See also

"Power Analysis Attacks" by Mangard et. al. p. 228 ff.

Parameters

[in,out]

mixColMasks

( mask_t): Masks m_i & m_i'.

invMaskState()

void Masking::invMaskState

(

state_t

state

)

const

(Inverse) mask the state before the first AddRoundKey step.

XOR the state with (m_i' ^ m ^ m'), i=1..4.

See also

"Power Analysis Attacks" by Mangard et. al. p. 228 ff.

Parameters

[in,out]

state

( state_t): State to be masked.

invReMaskState()

void Masking::invReMaskState

(

state_t

state

)

const

(Inverse) re-mask the state after every MixCol step.

XOR the state with (m_i ^ m'), i=1..4.

See also

"Power Analysis Attacks" by Mangard et. al. p. 228 ff.

Parameters

[in,out]

state

( state_t): State to be re-masked.

invUnMaskState()

void Masking::invUnMaskState

(

state_t

state

)

const

(Inverse) un-mask the state after the last AddRoundKey step.

XOR the state mit m_i', i=1..4.

See also

"Power Analysis Attacks" by Mangard et. al. p. 228 ff.

Parameters

[in,out]

state

( state_t): State to be un-masked.

maskSubKeys()

void Masking::maskSubKeys	(	const sub_keys_t	subKeys,
		sub_keys_t	maskedSubKeys
	)		const

Mask the subKeys & store the masked keys in maskedSubKeys.

XOR the original keys with masks (m_i' ^ m), i=1..4.

See also

"Power Analysis Attacks" by Mangard et. al. p. 228 ff.

Parameters

[in]	subKeys	(const sub_keys_t): Original sub-keys to be masked.
[out]	maskedSubKeys	( sub_keys_t): Masked sub-keys.

Member Data Documentation

mMixColMasks

mask_t Masking::mMixColMasks[4] = {}

private

4 MixCol input & output masks.

In "Power Analysis Attacks" by Mangard et. al. p. 228 ff., the MixCol input masks are noted as m_i, while the output masks are noted as m_i', where i=1..4.

mSubByteMask

mask_t Masking::mSubByteMask = {}

private

SubByte input & output mask.

In "Power Analysis Attacks" by Mangard et. al. p. 228 ff., the SubByte mask input mask is noted as m, while the output mask is noted as m'.

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The documentation for this class was generated from the following file:

• masking.h