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arduinolibs/libraries/Crypto/SpeckLowMemory.cpp

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/*
* Copyright (C) 2015 Southern Storm Software, Pty Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include "SpeckLowMemory.h"
#include "Crypto.h"
#include "utility/RotateUtil.h"
#include "utility/EndianUtil.h"
#include <string.h>
/**
* \class SpeckLowMemory SpeckLowMemory.h <SpeckLowMemory.h>
* \brief Speck block cipher with a 128-bit block size (low-memory version).
*
* This class differs from the Speck class in the following ways:
*
* \li RAM requirements are vastly reduced. The key (up to 256 bits) is
* stored directly and then expanded to the full key schedule round by round.
* The setKey() method is very fast because of this.
* \li Performance of encryptBlock() is slower than for Speck due to
* expanding the key on the fly rather than ahead of time.
* \li The decryptBlock() function is not supported, which means that CBC
* mode cannot be used but the CTR, CFB, OFB, and GCM modes can be used.
*
* This class is useful when RAM is at a premium, CBC mode is not required,
* and reduced encryption performance is not a hindrance to the application.
* Even though the performance of encryptBlock() is reduced, this class is
* still faster than AES with equivalent key sizes.
*
* See the documentation for the Speck class for more information on the
* Speck family of block ciphers.
*
* References: https://en.wikipedia.org/wiki/Speck_%28cipher%29,
* http://eprint.iacr.org/2013/404
*
* \sa Speck
*/
// The "avr-gcc" compiler doesn't do a very good job of compiling
// code involving 64-bit values. So we have to use inline assembly.
// It also helps to break the state up into 32-bit quantities
// because "asm" supports register names like %A0, %B0, %C0, %D0
// for the bytes in a 32-bit quantity, but it does not support
// %E0, %F0, %G0, %H0 for the high bytes of a 64-bit quantity.
#if defined(__AVR__)
#define USE_AVR_INLINE_ASM 1
#endif
/**
* \brief Constructs a low-memory Speck block cipher with no initial key.
*
* This constructor must be followed by a call to setKey() before the
* block cipher can be used for encryption.
*/
SpeckLowMemory::SpeckLowMemory()
: rounds(32)
{
}
SpeckLowMemory::~SpeckLowMemory()
{
clean(k);
}
size_t SpeckLowMemory::blockSize() const
{
return 16;
}
size_t SpeckLowMemory::keySize() const
{
// Also supports 128-bit and 192-bit, but we only report 256-bit.
return 32;
}
// Pack/unpack byte-aligned big-endian 64-bit quantities.
#define pack64(data, value) \
do { \
uint64_t v = htobe64((value)); \
memcpy((data), &v, sizeof(uint64_t)); \
} while (0)
#define unpack64(value, data) \
do { \
memcpy(&(value), (data), sizeof(uint64_t)); \
(value) = be64toh((value)); \
} while (0)
bool SpeckLowMemory::setKey(const uint8_t *key, size_t len)
{
#if USE_AVR_INLINE_ASM
// Determine the number of rounds to use and validate the key length.
if (len == 32) {
rounds = 34;
} else if (len == 24) {
rounds = 33;
} else if (len == 16) {
rounds = 32;
} else {
return false;
}
// Copy the bytes of the key into the "k" array in reverse order to
// convert big endian into little-endian.
__asm__ __volatile__ (
"1:\n"
"ld __tmp_reg__,-Z\n"
"st X+,__tmp_reg__\n"
"dec %2\n"
"brne 1b\n"
: : "x"(k), "z"(key + len), "r"(len)
);
#else
if (len == 32) {
rounds = 34;
unpack64(k[3], key);
unpack64(k[2], key + 8);
unpack64(k[1], key + 16);
unpack64(k[0], key + 24);
} else if (len == 24) {
rounds = 33;
unpack64(k[2], key);
unpack64(k[1], key + 8);
unpack64(k[0], key + 16);
} else if (len == 16) {
rounds = 32;
unpack64(k[1], key);
unpack64(k[0], key + 8);
} else {
return false;
}
#endif
return true;
}
void SpeckLowMemory::encryptBlock(uint8_t *output, const uint8_t *input)
{
#if USE_AVR_INLINE_ASM
uint64_t l[4];
uint32_t xlow, xhigh, ylow, yhigh;
uint32_t slow, shigh;
uint8_t li_in = 0;
uint8_t li_out = (rounds - 31) * 8;
// Copy the "k" array into "s" and the "l" array.
__asm__ __volatile__ (
"ldd r25,%4\n" // r25 = li_out
"ld __tmp_reg__,Z+\n"
"std %A0,__tmp_reg__\n"
"ld __tmp_reg__,Z+\n"
"std %B0,__tmp_reg__\n"
"ld __tmp_reg__,Z+\n"
"std %C0,__tmp_reg__\n"
"ld __tmp_reg__,Z+\n"
"std %D0,__tmp_reg__\n"
"ld __tmp_reg__,Z+\n"
"std %A1,__tmp_reg__\n"
"ld __tmp_reg__,Z+\n"
"std %B1,__tmp_reg__\n"
"ld __tmp_reg__,Z+\n"
"std %C1,__tmp_reg__\n"
"ld __tmp_reg__,Z+\n"
"std %D1,__tmp_reg__\n"
"1:\n" // l[0..] = k[1..]
"ld __tmp_reg__,Z+\n"
"st X+,__tmp_reg__\n"
"dec r25\n"
"brne 1b\n"
: "=Q"(slow), "=Q"(shigh)
: "z"(k), "x"(l), "Q"(li_out)
: "r25"
);
// Unpack the input into the x and y variables, converting
// from big-endian into little-endian in the process.
__asm__ __volatile__ (
"ld %D1,Z\n"
"ldd %C1,Z+1\n"
"ldd %B1,Z+2\n"
"ldd %A1,Z+3\n"
"ldd %D0,Z+4\n"
"ldd %C0,Z+5\n"
"ldd %B0,Z+6\n"
"ldd %A0,Z+7\n"
"ldd %D3,Z+8\n"
"ldd %C3,Z+9\n"
"ldd %B3,Z+10\n"
"ldd %A3,Z+11\n"
"ldd %D2,Z+12\n"
"ldd %C2,Z+13\n"
"ldd %B2,Z+14\n"
"ldd %A2,Z+15\n"
: "=r"(xlow), "=r"(xhigh), "=r"(ylow), "=r"(yhigh)
: "z"(input)
);
// Perform all encryption rounds while expanding the key schedule in-place.
__asm__ __volatile__ (
"mov r23,__zero_reg__\n" // i = 0
"1:\n"
// Adjust x and y for this round using the key schedule word s.
// x = (rightRotate8_64(x) + y) ^ s;
"mov __tmp_reg__,%A0\n" // x = rightRotate8_64(x)
"mov %A0,%B0\n"
"mov %B0,%C0\n"
"mov %C0,%D0\n"
"mov %D0,%A1\n"
"mov %A1,%B1\n"
"mov %B1,%C1\n"
"mov %C1,%D1\n"
"mov %D1,__tmp_reg__\n"
"add %A0,%A2\n" // x += y
"adc %B0,%B2\n"
"adc %C0,%C2\n"
"adc %D0,%D2\n"
"adc %A1,%A3\n"
"adc %B1,%B3\n"
"adc %C1,%C3\n"
"adc %D1,%D3\n"
"ldd __tmp_reg__,%A4\n" // x ^= s
"eor %A0,__tmp_reg__\n"
"ldd __tmp_reg__,%B4\n"
"eor %B0,__tmp_reg__\n"
"ldd __tmp_reg__,%C4\n"
"eor %C0,__tmp_reg__\n"
"ldd __tmp_reg__,%D4\n"
"eor %D0,__tmp_reg__\n"
"ldd __tmp_reg__,%A5\n"
"eor %A1,__tmp_reg__\n"
"ldd __tmp_reg__,%B5\n"
"eor %B1,__tmp_reg__\n"
"ldd __tmp_reg__,%C5\n"
"eor %C1,__tmp_reg__\n"
"ldd __tmp_reg__,%D5\n"
"eor %D1,__tmp_reg__\n"
// y = leftRotate3_64(y) ^ x;
"lsl %A2\n" // y = leftRotate1_64(y)
"rol %B2\n"
"rol %C2\n"
"rol %D2\n"
"rol %A3\n"
"rol %B3\n"
"rol %C3\n"
"rol %D3\n"
"adc %A2,__zero_reg__\n"
"lsl %A2\n" // y = leftRotate1_64(y)
"rol %B2\n"
"rol %C2\n"
"rol %D2\n"
"rol %A3\n"
"rol %B3\n"
"rol %C3\n"
"rol %D3\n"
"adc %A2,__zero_reg__\n"
"lsl %A2\n" // y = leftRotate1_64(y)
"rol %B2\n"
"rol %C2\n"
"rol %D2\n"
"rol %A3\n"
"rol %B3\n"
"rol %C3\n"
"rol %D3\n"
"adc %A2,__zero_reg__\n"
"eor %A2,%A0\n" // y ^= x
"eor %B2,%B0\n"
"eor %C2,%C0\n"
"eor %D2,%D0\n"
"eor %A3,%A1\n"
"eor %B3,%B1\n"
"eor %C3,%C1\n"
"eor %D3,%D1\n"
// On the last round we don't need to compute s so we
// can exit early here if (i + 1) == rounds.
"mov __tmp_reg__,r23\n" // temp = i + 1
"inc __tmp_reg__\n"
"cp __tmp_reg__,%9\n" // if (temp == rounds) ...
"brne 2f\n"
"rjmp 3f\n"
"2:\n"
// Save x and y on the stack so we can reuse registers for t and s.
"push %A0\n"
"push %B0\n"
"push %C0\n"
"push %D0\n"
"push %A1\n"
"push %B1\n"
"push %C1\n"
"push %D1\n"
"push %A2\n"
"push %B2\n"
"push %C2\n"
"push %D2\n"
"push %A3\n"
"push %B3\n"
"push %C3\n"
"push %D3\n"
// Compute the key schedule word s for the next round.
// l[li_out] = (s + rightRotate8_64(l[li_in])) ^ i;
"ldd r24,%6\n" // Z = &(l[li_in])
"add %A8,r24\n"
"adc %B8,__zero_reg__\n"
"ld %D1,Z+\n" // t = rightRotate8_64(l[li_in])
"ld %A0,Z+\n"
"ld %B0,Z+\n"
"ld %C0,Z+\n"
"ld %D0,Z+\n"
"ld %A1,Z+\n"
"ld %B1,Z+\n"
"ld %C1,Z+\n"
"ldd %A2,%A4\n" // load s
"ldd %B2,%B4\n"
"ldd %C2,%C4\n"
"ldd %D2,%D4\n"
"ldd %A3,%A5\n"
"ldd %B3,%B5\n"
"ldd %C3,%C5\n"
"ldd %D3,%D5\n"
"add %A0,%A2\n" // t += s
"adc %B0,%B2\n"
"adc %C0,%C2\n"
"adc %D0,%D2\n"
"adc %A1,%A3\n"
"adc %B1,%B3\n"
"adc %C1,%C3\n"
"adc %D1,%D3\n"
"eor %A0,r23\n" // t ^= i
// Z = Z - li_in + li_out
"ldi r25,8\n" // li_in = li_in + 1
"add r24,r25\n"
"sub %A8,r24\n" // return Z to its initial value
"sbc %B8,__zero_reg__\n"
"andi r24,0x1f\n" // li_in = li_in % 4
"std %6,r24\n"
"ldd r24,%7\n" // Z = &(l[li_out])
"add %A8,r24\n"
"adc %B8,__zero_reg__\n"
"st Z+,%A0\n" // l[li_out] = t
"st Z+,%B0\n"
"st Z+,%C0\n"
"st Z+,%D0\n"
"st Z+,%A1\n"
"st Z+,%B1\n"
"st Z+,%C1\n"
"st Z+,%D1\n"
"add r24,r25\n" // li_out = li_out + 1
"sub %A8,r24\n" // return Z to its initial value
"sbc %B8,__zero_reg__\n"
"andi r24,0x1f\n" // li_out = li_out % 4
"std %7,r24\n"
// s = leftRotate3_64(s) ^ l[li_out];
"lsl %A2\n" // s = leftRotate1_64(s)
"rol %B2\n"
"rol %C2\n"
"rol %D2\n"
"rol %A3\n"
"rol %B3\n"
"rol %C3\n"
"rol %D3\n"
"adc %A2,__zero_reg__\n"
"lsl %A2\n" // s = leftRotate1_64(s)
"rol %B2\n"
"rol %C2\n"
"rol %D2\n"
"rol %A3\n"
"rol %B3\n"
"rol %C3\n"
"rol %D3\n"
"adc %A2,__zero_reg__\n"
"lsl %A2\n" // s = leftRotate1_64(s)
"rol %B2\n"
"rol %C2\n"
"rol %D2\n"
"rol %A3\n"
"rol %B3\n"
"rol %C3\n"
"rol %D3\n"
"adc %A2,__zero_reg__\n"
"eor %A2,%A0\n" // s ^= l[li_out]
"eor %B2,%B0\n"
"eor %C2,%C0\n"
"eor %D2,%D0\n"
"eor %A3,%A1\n"
"eor %B3,%B1\n"
"eor %C3,%C1\n"
"eor %D3,%D1\n"
"std %A4,%A2\n" // store s
"std %B4,%B2\n"
"std %C4,%C2\n"
"std %D4,%D2\n"
"std %A5,%A3\n"
"std %B5,%B3\n"
"std %C5,%C3\n"
"std %D5,%D3\n"
// Pop registers from the stack to recover the x and y values.
"pop %D3\n"
"pop %C3\n"
"pop %B3\n"
"pop %A3\n"
"pop %D2\n"
"pop %C2\n"
"pop %B2\n"
"pop %A2\n"
"pop %D1\n"
"pop %C1\n"
"pop %B1\n"
"pop %A1\n"
"pop %D0\n"
"pop %C0\n"
"pop %B0\n"
"pop %A0\n"
// Bottom of the loop.
"inc r23\n"
"rjmp 1b\n"
"3:\n"
: "+r"(xlow), "+r"(xhigh), "+r"(ylow), "+r"(yhigh),
"+Q"(slow), "+Q"(shigh), "+Q"(li_in), "+Q"(li_out)
: "z"(l), "r"(rounds)
: "r23", "r24", "r25"
);
// Pack the results into the output and convert back to big-endian.
__asm__ __volatile__ (
"st Z,%D1\n"
"std Z+1,%C1\n"
"std Z+2,%B1\n"
"std Z+3,%A1\n"
"std Z+4,%D0\n"
"std Z+5,%C0\n"
"std Z+6,%B0\n"
"std Z+7,%A0\n"
"std Z+8,%D3\n"
"std Z+9,%C3\n"
"std Z+10,%B3\n"
"std Z+11,%A3\n"
"std Z+12,%D2\n"
"std Z+13,%C2\n"
"std Z+14,%B2\n"
"std Z+15,%A2\n"
: : "r"(xlow), "r"(xhigh), "r"(ylow), "r"(yhigh), "z"(output)
);
#else
uint64_t l[4];
uint64_t x, y, s;
uint8_t round;
uint8_t li_in = 0;
uint8_t li_out = rounds - 31;
uint8_t i = 0;
// Copy the input block into the work registers.
unpack64(x, input);
unpack64(y, input + 8);
// Prepare the key schedule.
memcpy(l, k + 1, li_out * sizeof(uint64_t));
s = k[0];
// Perform all encryption rounds except the last.
for (round = rounds - 1; round > 0; --round, ++i) {
// Perform the round with the current key schedule word.
x = (rightRotate8_64(x) + y) ^ s;
y = leftRotate3_64(y) ^ x;
// Calculate the next key schedule word.
l[li_out] = (s + rightRotate8_64(l[li_in])) ^ i;
s = leftRotate3_64(s) ^ l[li_out];
li_in = (li_in + 1) & 0x03;
li_out = (li_out + 1) & 0x03;
}
// Perform the final round and copy to the output.
x = (rightRotate8_64(x) + y) ^ s;
y = leftRotate3_64(y) ^ x;
pack64(output, x);
pack64(output + 8, y);
#endif
}
/**
* \brief Decrypts a single block using this cipher.
*
* \param output The output buffer to put the plaintext into.
* Must be at least blockSize() bytes in length.
* \param input The input buffer to read the ciphertext from which is
* allowed to overlap with \a output. Must be at least blockSize()
* bytes in length.
*
* \note This function is not supported for SpeckLowMemory, which means
* that CBC mode cannot be used but that the CTR, CFB, OFB, and GCM modes
* can be used.
*/
void SpeckLowMemory::decryptBlock(uint8_t *output, const uint8_t *input)
{
// Decryption is not supported.
}
void SpeckLowMemory::clear()
{
clean(k);
}
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