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Remove use of coerceSize following release of Cryptol 3.2.0 #127

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Remove use of coerceSize following release of Cryptol 3.2.0 #127

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42 changes: 9 additions & 33 deletions Primitive/Asymmetric/Cipher/ML-KEM/specification.cry
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Original file line number Diff line number Diff line change
Expand Up @@ -153,8 +153,6 @@ NaiveNTTInv f = [term*(recip 128) | term <- ParametricNTTInv f (recip zeta)]
// This section Copyright Amazon.com, Inc. or its affiliates.
//////////////////////////////////////////////////////////////

import Common::utils (coerceSize)

// Simple lookup table for Zeta value given K
zeta_expc : [128](Z q)
zeta_expc = [ 1, 1729, 2580, 3289, 2642, 630, 1897, 848,
Expand All @@ -175,16 +173,6 @@ zeta_expc = [ 1, 1729, 2580, 3289, 2642, 630, 1897, 848,
1722, 1212, 1874, 1029, 2110, 2935, 885, 2154 ]

// Fast recursive CT-NTT
//
// The "coerceSize" calls in this code are required to satisfy
// Cryptol's type constraint solver that this code really
// is type-correct by effectively changing a static type-check
// into a dynamic one.
//
// As the static type constraint prover improves, this
// might become unncessesary.
//
// See https://github.com/GaloisInc/cryptol/issues/1489 for more details.
ct_butterfly :
{m, hm}
(m >= 2, m <= 8, hm >= 1, hm <= 7, hm == m - 1) =>
Expand All @@ -195,7 +183,7 @@ ct_butterfly v z = new_v
lower, upper : [2^^hm](Z q)
lower@x = v@x + z * v@(x + halflen)
upper@x = v@x - z * v@(x + halflen)
new_v = coerceSize (lower # upper)
new_v = lower # upper

fast_nttl :
{lv} // Length of v is a member of {256,128,64,32,16,8,4}
Expand All @@ -206,30 +194,19 @@ fast_nttl v k
| lv == 2 => ct_butterfly`{lv,lv-1} v (zeta_expc@k)

// Recursive case. Butterfly what we have, then recurse on each half,
// concatenate the results and return. As above, we need coerceSize
// here (twice) to satisfy the type checker.
| lv > 2 => coerceSize ((fast_nttl`{lv-1} s0 (k * 2)) #
(fast_nttl`{lv-1} s1 (k * 2 + 1)))
// concatenate the results and return.
| lv > 2 => (fast_nttl`{lv-1} s0 (k * 2)) #
(fast_nttl`{lv-1} s1 (k * 2 + 1))
where
t = ct_butterfly`{lv,lv-1} v (zeta_expc@k)
// Split t into two halves s0 and s1
[s0, s1] = split (coerceSize t)
[s0, s1] = split t

// Top level entry point - start with lv=256, k=1
fast_ntt : Z_q_256 -> Z_q_256
fast_ntt v = fast_nttl v 1

// Fast recursive GS-Inverse-NTT
//
// The "coerceSize" calls in this code are required to satisfy
// Cryptol's type constraint solver that this code really
// is type-correct by effectively changing a static type-check
// into a dynamic one.
//
// As the static type constraint prover improves, this
// might become unncessesary.
//
// See https://github.com/GaloisInc/cryptol/issues/1489 for more details.
gs_butterfly :
{m, hm}
(m >= 2, m <= 8, hm >= 1, hm <= 7, hm == m - 1) =>
Expand All @@ -240,7 +217,7 @@ gs_butterfly v z = new_v
lower, upper : [2^^hm](Z q)
lower@x = v@x + v@(x + halflen)
upper@x = z * (v@(x + halflen) - v@x)
new_v = coerceSize (lower # upper)
new_v = lower # upper

fast_invnttl :
{lv} // Length of v is a member of {256,128,64,32,16,8,4}
Expand All @@ -253,13 +230,12 @@ fast_invnttl v k

// Recursive case. Recurse on each half,
// concatenate the results, butterfly that, and return.
// As above, we need coerceSize here (twice) to satisfy the type checker.
| lv > 2 => gs_butterfly`{lv,lv-1} t (zeta_expc@k)
where
// Split t into two halves s0 and s1
[s0, s1] = split (coerceSize v)
t = coerceSize ((fast_invnttl`{lv-1} s0 (k * 2 + 1)) #
(fast_invnttl`{lv-1} s1 (k * 2)))
[s0, s1] = split v
t = (fast_invnttl`{lv-1} s0 (k * 2 + 1)) #
(fast_invnttl`{lv-1} s1 (k * 2))

// Multiply all elements of v by the reciprocal of 128 (modulo q)
recip_128_modq = (recip 128) : (Z q)
Expand Down