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C nettle, low-level cryptographics library
C
C Copyright (C) 2013 Niels Möller
C
C The nettle library is free software; you can redistribute it and/or modify
C it under the terms of the GNU Lesser General Public License as published by
C the Free Software Foundation; either version 2.1 of the License, or (at your
C option) any later version.
C
C The nettle library is distributed in the hope that it will be useful, but
C WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
C or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
C License for more details.
C
C You should have received a copy of the GNU Lesser General Public License
C along with the nettle library; see the file COPYING.LIB. If not, write to
C the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
C MA 02111-1301, USA.
.file "poly1305-internal.asm"
C Registers mainly used by poly1305_block
define(<CTX>, <%rdi>)
define(<T0>, <%rcx>)
define(<T1>, <%rsi>)
define(<T2>, <%r8>)
define(<H0>, <%r9>)
define(<H1>, <%r10>)
define(<H2>, <%r11>)
C poly1305_set_key(struct poly1305_ctx *ctx, const uint8_t key[16])
.text
C Registers:
C %rdi: ctx
C %rsi: key
C %r8: mask
ALIGN(16)
PROLOGUE(nettle_poly1305_set_key)
W64_ENTRY(2,0)
mov $0x0ffffffc0fffffff, %r8
mov (%rsi), %rax
and %r8, %rax
and $-4, %r8
mov %rax, (CTX)
mov 8(%rsi), %rax
and %r8, %rax
mov %rax, P1305_R1 (CTX)
shr $2, %rax
imul $5, %rax
mov %rax, P1305_S1 (CTX)
xor XREG(%rax), XREG(%rax)
mov %rax, P1305_H0 (CTX)
mov %rax, P1305_H1 (CTX)
mov XREG(%rax), P1305_H2 (CTX)
W64_EXIT(2,0)
ret
EPILOGUE(nettle_poly1305_set_key)
C 64-bit multiplication mod 2^130 - 5
C
C (x_0 + B x_1 + B^2 x_2) * (r_0 + B r_1) =
C 1 B B^2 B^3
C x_0 r_0
C x_0 r_1
C x_1 r_0
C x_1 r_1
C x_2 r_0
C x_2 r_1
C Then r_1 B^2 = r_1/4 (2^130) = 5/4 r_1.
C and r_1 B^3 = 5/4 B r_1
C So we get
C
C x_0 r_0 + x_1 (5/4 r_1) + B (x_0 r_1 + x_1 r_0 + x_2 5/4 r_1 + B x_2 r_0)
C 1 B B^2 B^3
C x_0 r_0
C x_1 r'_1
C x_0 r_1
C x_1 r_0
C x_2 r'_1
C x_2 r_0
C _poly1305_block (struct poly1305_ctx *ctx, const uint8_t m[16], unsigned hi)
PROLOGUE(_nettle_poly1305_block)
W64_ENTRY(3, 0)
mov (%rsi), T0
mov 8(%rsi), T1
mov XREG(%rdx), XREG(T2)
C Registers:
C Inputs: CTX, T0, T1, T2,
C Outputs: H0, H1, H2, stored into the context.
add P1305_H0 (CTX), T0
adc P1305_H1 (CTX), T1
adc P1305_H2 (CTX), XREG(T2)
mov P1305_R0 (CTX), %rax
mul T0 C x0*r0
mov %rax, H0
mov %rdx, H1
mov P1305_S1 (CTX), %rax C 5/4 r1
mov %rax, H2
mul T1 C x1*r1'
imul T2, H2 C x2*r1'
imul P1305_R0 (CTX), T2 C x2*r0
add %rax, H0
adc %rdx, H1
mov P1305_R0 (CTX), %rax
mul T1 C x1*r0
add %rax, H2
adc %rdx, T2
mov P1305_R1 (CTX), %rax
mul T0 C x0*r1
add %rax, H2
adc %rdx, T2
mov T2, %rax
shr $2, %rax
imul $5, %rax
and $3, XREG(T2)
add %rax, H0
adc H2, H1
adc $0, XREG(T2)
mov H0, P1305_H0 (CTX)
mov H1, P1305_H1 (CTX)
mov XREG(T2), P1305_H2 (CTX)
W64_EXIT(3, 0)
ret
EPILOGUE(_nettle_poly1305_block)
C poly1305_digest (struct poly1305_ctx *ctx, uint8_t *s)
C Registers:
C %rdi: ctx
C %rsi: s
PROLOGUE(nettle_poly1305_digest)
W64_ENTRY(2, 0)
mov P1305_H0 (CTX), H0
mov P1305_H1 (CTX), H1
mov P1305_H2 (CTX), XREG(H2)
mov XREG(H2), XREG(%rax)
shr $2, XREG(%rax)
and $3, H2
imul $5, XREG(%rax)
add %rax, H0
adc $0, H1
adc $0, XREG(H2)
C Use %rax instead of %rsi
define(<T1>, <%rax>)
C Add 5, use result if >= 2^130
mov $5, T0
xor T1, T1
add H0, T0
adc H1, T1
adc $0, XREG(H2)
cmp $4, XREG(H2)
cmovnc T0, H0
cmovnc T1, H1
add H0, (%rsi)
adc H1, 8(%rsi)
xor XREG(%rax), XREG(%rax)
mov %rax, P1305_H0 (CTX)
mov %rax, P1305_H1 (CTX)
mov XREG(%rax), P1305_H2 (CTX)
W64_EXIT(2, 0)
ret
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