1package poseidon
  2
  3import (
  4	. "gnark-ed25519/field"
  5
  6	"github.com/consensys/gnark/frontend"
  7)
  8
  9const HALF_N_FULL_ROUNDS = 4
 10const N_FULL_ROUNDS_TOTAL = 2 * HALF_N_FULL_ROUNDS
 11const N_PARTIAL_ROUNDS = 22
 12const N_ROUNDS = N_FULL_ROUNDS_TOTAL + N_PARTIAL_ROUNDS
 13const MAX_WIDTH = 12
 14const WIDTH = 12
 15const SPONGE_WIDTH = 12
 16const SPONGE_RATE = 8
 17
 18type PoseidonState = [WIDTH]F
 19type PoseidonChip struct {
 20	api   frontend.API
 21	field frontend.API
 22}
 23
 24func NewPoseidonChip(api frontend.API, field frontend.API) *PoseidonChip {
 25	return &PoseidonChip{api: api, field: field}
 26}
 27
 28func (c *PoseidonChip) Poseidon(input PoseidonState) PoseidonState {
 29	state := input
 30	roundCounter := 0
 31	state = c.fullRounds(state, &roundCounter)
 32	state = c.partialRounds(state, &roundCounter)
 33	state = c.fullRounds(state, &roundCounter)
 34	return state
 35}
 36
 37func (c *PoseidonChip) HashNToMNoPad(input []F, nbOutputs int) []F {
 38	var state PoseidonState
 39
 40	for i := 0; i < len(input); i += SPONGE_RATE {
 41		for j := 0; j < SPONGE_RATE; j++ {
 42			if i+j < len(input) {
 43				state[j] = input[i+j]
 44			}
 45		}
 46		state = c.Poseidon(state)
 47	}
 48
 49	var outputs []F
 50
 51	for {
 52		for i := 0; i < SPONGE_RATE; i++ {
 53			outputs = append(outputs, state[i])
 54			if len(outputs) == nbOutputs {
 55				return outputs
 56			}
 57		}
 58		state = c.Poseidon(state)
 59	}
 60}
 61
 62func (c *PoseidonChip) HashNoPad(input []F) Hash {
 63	var hash Hash
 64	copy(hash[:], c.HashNToMNoPad(input, 4))
 65	return hash
 66}
 67
 68func (c *PoseidonChip) fullRounds(state PoseidonState, roundCounter *int) PoseidonState {
 69	for i := 0; i < HALF_N_FULL_ROUNDS; i++ {
 70		state = c.constantLayer(state, roundCounter)
 71		state = c.sBoxLayer(state)
 72		state = c.mdsLayer(state)
 73		*roundCounter += 1
 74	}
 75	return state
 76}
 77
 78func (c *PoseidonChip) partialRounds(state PoseidonState, roundCounter *int) PoseidonState {
 79	state = c.partialFirstConstantLayer(state)
 80	state = c.mdsPartialLayerInit(state)
 81
 82	for i := 0; i < N_PARTIAL_ROUNDS; i++ {
 83		state[0] = c.sBoxMonomial(state[0])
 84		state[0] = c.field.Add(state[0], FAST_PARTIAL_ROUND_CONSTANTS[i]).(F)
 85		state = c.mdsPartialLayerFast(state, i)
 86	}
 87
 88	*roundCounter += N_PARTIAL_ROUNDS
 89
 90	return state
 91}
 92
 93func (c *PoseidonChip) constantLayer(state PoseidonState, roundCounter *int) PoseidonState {
 94	for i := 0; i < 12; i++ {
 95		if i < WIDTH {
 96			roundConstant := NewFieldElement(ALL_ROUND_CONSTANTS[i+WIDTH*(*roundCounter)])
 97			state[i] = c.field.Add(state[i], roundConstant).(F)
 98		}
 99	}
100	return state
101}
102
103func (c *PoseidonChip) sBoxLayer(state PoseidonState) PoseidonState {
104	for i := 0; i < 12; i++ {
105		if i < WIDTH {
106			state[i] = c.sBoxMonomial(state[i])
107		}
108	}
109	return state
110}
111
112func (c *PoseidonChip) sBoxMonomial(x F) F {
113	x2 := c.field.Mul(x, x)
114	x4 := c.field.Mul(x2, x2)
115	x3 := c.field.Mul(x2, x)
116	return c.field.Mul(x3, x4).(F)
117}
118
119func (c *PoseidonChip) mdsRowShf(r int, v [WIDTH]frontend.Variable) frontend.Variable {
120	res := frontend.Variable(0)
121
122	for i := 0; i < 12; i++ {
123		if i < WIDTH {
124			res1 := c.api.Mul(v[(i+r)%WIDTH], frontend.Variable(MDS_MATRIX_CIRC[i]))
125			res = c.api.Add(res, res1)
126		}
127	}
128
129	res = c.api.Add(res, c.api.Mul(v[r], MDS_MATRIX_DIAG[r]))
130	return res
131}
132
133func (c *PoseidonChip) mdsLayer(state_ PoseidonState) PoseidonState {
134	var result PoseidonState
135	for i := 0; i < WIDTH; i++ {
136		result[i] = NewFieldElement(0)
137	}
138
139	var state [WIDTH]frontend.Variable
140	for i := 0; i < WIDTH; i++ {
141		state[i] = c.api.FromBinary(c.field.ToBinary(state_[i])...)
142	}
143
144	for r := 0; r < 12; r++ {
145		if r < WIDTH {
146			sum := c.mdsRowShf(r, state)
147			bits := c.api.ToBinary(sum)
148			result[r] = c.field.FromBinary(bits).(F)
149		}
150	}
151
152	return result
153}
154
155func (c *PoseidonChip) partialFirstConstantLayer(state PoseidonState) PoseidonState {
156	for i := 0; i < 12; i++ {
157		if i < WIDTH {
158			state[i] = c.field.Add(state[i], NewFieldElement(FAST_PARTIAL_FIRST_ROUND_CONSTANT[i])).(F)
159		}
160	}
161	return state
162}
163
164func (c *PoseidonChip) mdsPartialLayerInit(state PoseidonState) PoseidonState {
165	var result PoseidonState
166	for i := 0; i < 12; i++ {
167		result[i] = NewFieldElement(0)
168	}
169
170	result[0] = state[0]
171
172	for r := 1; r < 12; r++ {
173		if r < WIDTH {
174			for d := 1; d < 12; d++ {
175				if d < WIDTH {
176					t := NewFieldElement(FAST_PARTIAL_ROUND_INITIAL_MATRIX[r-1][d-1])
177					result[d] = c.field.Add(result[d], c.field.Mul(state[r], t)).(F)
178				}
179			}
180		}
181	}
182
183	return result
184}
185
186func (c *PoseidonChip) mdsPartialLayerFast(state PoseidonState, r int) PoseidonState {
187	dSum := frontend.Variable(0)
188	for i := 1; i < 12; i++ {
189		if i < WIDTH {
190			t := frontend.Variable(FAST_PARTIAL_ROUND_W_HATS[r][i-1])
191			si := c.api.FromBinary(c.field.ToBinary(state[i])...)
192			dSum = c.api.Add(dSum, c.api.Mul(si, t))
193		}
194	}
195
196	s0 := c.api.FromBinary(c.field.ToBinary(state[0])...)
197	mds0to0 := frontend.Variable(MDS_MATRIX_CIRC[0] + MDS_MATRIX_DIAG[0])
198	dSum = c.api.Add(dSum, c.api.Mul(s0, mds0to0))
199	d := c.field.FromBinary(c.api.ToBinary(dSum))
200
201	var result PoseidonState
202	for i := 0; i < WIDTH; i++ {
203		result[i] = NewFieldElement(0)
204	}
205
206	result[0] = d.(F)
207
208	for i := 1; i < 12; i++ {
209		if i < WIDTH {
210			t := NewFieldElement(FAST_PARTIAL_ROUND_VS[r][i-1])
211			result[i] = c.field.Add(state[i], c.field.Mul(state[0], t)).(F)
212		}
213	}
214
215	return result
216}