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@ -1,7 +1,6 @@ |
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package poseidon |
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import ( |
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"errors" |
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"fmt" |
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"math/big" |
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@ -17,40 +16,41 @@ func zero() *ff.Element { |
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return ff.NewElement() |
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} |
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// ark computes Add-Round Key, from the paper https://eprint.iacr.org/2019/458.pdf
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func ark(state []*ff.Element, c []*ff.Element, it int) { |
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for i := 0; i < len(state); i++ { |
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state[i].Add(state[i], c[it+i]) |
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} |
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} |
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// exp5 performs x^5 mod p
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// https://eprint.iacr.org/2019/458.pdf page 8
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func exp5(a *ff.Element) { |
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a.Exp(*a, 5) |
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} |
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// sbox https://eprint.iacr.org/2019/458.pdf page 6
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func sbox(nRoundsF, nRoundsP int, state []*ff.Element, i int) { |
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if (i < nRoundsF/2) || (i >= nRoundsF/2+nRoundsP) { |
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for j := 0; j < len(state); j++ { |
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exp5(state[j]) |
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} |
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} else { |
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exp5(state[0]) |
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// exp5state perform exp5 for whole state
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func exp5state(state []*ff.Element) { |
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for i := 0; i < len(state); i++ { |
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exp5(state[i]) |
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} |
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} |
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// ark computes Add-Round Key, from the paper https://eprint.iacr.org/2019/458.pdf
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func ark(state []*ff.Element, c []*ff.Element, it int) { |
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for i := 0; i < len(state); i++ { |
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state[i].Add(state[i], c[it+i]) |
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} |
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} |
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// mix returns [[matrix]] * [vector]
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func mix(state []*ff.Element, newState []*ff.Element, m [][]*ff.Element) { |
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func mix(state []*ff.Element, t int, m [][]*ff.Element) []*ff.Element { |
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mul := zero() |
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newState := make([]*ff.Element, t) |
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for i := 0; i < t; i++ { |
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newState[i] = zero() |
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} |
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for i := 0; i < len(state); i++ { |
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newState[i].SetUint64(0) |
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for j := 0; j < len(state); j++ { |
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mul.Mul(m[i][j], state[j]) |
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mul.Mul(m[j][i], state[j]) |
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newState[i].Add(newState[i], mul) |
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} |
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} |
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return newState |
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} |
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// Hash computes the Poseidon hash for the given inputs
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@ -59,29 +59,56 @@ func Hash(inpBI []*big.Int) (*big.Int, error) { |
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if len(inpBI) == 0 || len(inpBI) >= len(NROUNDSP)-1 { |
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return nil, fmt.Errorf("invalid inputs length %d, max %d", len(inpBI), len(NROUNDSP)-1) |
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} |
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if !utils.CheckBigIntArrayInField(inpBI[:]) { |
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return nil, errors.New("inputs values not inside Finite Field") |
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} |
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inp := utils.BigIntArrayToElementArray(inpBI[:]) |
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nRoundsF := NROUNDSF |
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nRoundsP := NROUNDSP[t-2] |
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C := c.c[t-2] |
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S := c.s[t-2] |
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M := c.m[t-2] |
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P := c.p[t-2] |
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state := make([]*ff.Element, t) |
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state[0] = zero() |
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copy(state[1:], inp[:]) |
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nRoundsF := NROUNDSF |
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nRoundsP := NROUNDSP[t-2] |
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ark(state, C, 0) |
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newState := make([]*ff.Element, t) |
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for i := 0; i < t; i++ { |
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newState[i] = zero() |
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for i := 0; i < nRoundsF/2-1; i++ { |
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exp5state(state) |
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ark(state, C, (i+1)*t) |
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state = mix(state, t, M) |
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} |
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exp5state(state) |
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ark(state, C, (nRoundsF/2)*t) |
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state = mix(state, t, P) |
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for i := 0; i < nRoundsP; i++ { |
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exp5(state[0]) |
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state[0].Add(state[0], C[(nRoundsF/2+1)*t+i]) |
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mul := zero() |
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newState0 := zero() |
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for j := 0; j < len(state); j++ { |
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mul.Mul(S[(t*2-1)*i+j], state[j]) |
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newState0.Add(newState0, mul) |
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} |
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for k := 1; k < t; k++ { |
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mul = zero() |
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state[k] = state[k].Add(state[k], mul.Mul(state[0], S[(t*2-1)*i+t+k-1])) |
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} |
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state[0] = newState0 |
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} |
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// ARK --> SBox --> M, https://eprint.iacr.org/2019/458.pdf pag.5
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for i := 0; i < nRoundsF+nRoundsP; i++ { |
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ark(state, c.c[t-2], i*t) |
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sbox(nRoundsF, nRoundsP, state, i) |
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mix(state, newState, c.m[t-2]) |
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state, newState = newState, state |
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for i := 0; i < nRoundsF/2-1; i++ { |
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exp5state(state) |
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ark(state, C, (nRoundsF/2+1)*t+nRoundsP+i*t) |
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state = mix(state, t, M) |
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} |
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exp5state(state) |
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state = mix(state, t, M) |
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rE := state[0] |
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r := big.NewInt(0) |
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rE.ToBigIntRegular(r) |
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