To support EIP-2565 the following are some changes required to Geth:
In contracts.go, the pricing formula for ModExp should be replaced with the following logic:
// Calculate the gas cost of the operation
gas := new(big.Int).Set(math.BigMax(modLen, baseLen))
gas = gas.Add(gas, 7).Div(8) // this is an integer divide with ceiling
gas = gas.Mul(gas, gas) // this will square the value
gas.Mul(gas, math.BigMax(adjExpLen, big1))
gas.Div(gas, new(big.Int).SetUint64(params.ModExpQuadCoeffDiv))
gas=math.BigMax(gas, new(big.Int).Set(200)) // this sets a minimum gas of 200
if gas.BitLen() > 64 {
return math.MaxUint64
}
return gas.Uint64()
Also, in protocol_params.go line 123 ModExpQuadCoeffDiv should be changed from 20 to 3.
Below is a table with the updated test vectors
| Test Case | EIP-198 Pricing | New Pricing |
|---|---|---|
| modexp_nagydani_1_square | 204 | 200 |
| modexp_nagydani_1_qube | 204 | 200 |
| modexp_nagydani_1_pow0x10001 | 3276 | 341 |
| modexp_nagydani_2_square | 665 | 200 |
| modexp_nagydani_2_qube | 665 | 200 |
| modexp_nagydani_2_pow0x10001 | 10649 | 1365 |
| modexp_nagydani_3_square | 1894 | 341 |
| modexp_nagydani_3_qube | 1894 | 341 |
| modexp_nagydani_3_pow0x10001 | 30310 | 5461 |
| modexp_nagydani_4_square | 5580 | 1365 |
| modexp_nagydani_4_qube | 5580 | 1365 |
| modexp_nagydani_4_pow0x10001 | 89292 | 21845 |
| modexp_nagydani_5_square | 17868 | 5461 |
| modexp_nagydani_5_qube | 17868 | 5461 |
| modexp_nagydani_5_pow0x10001 | 285900 | 87381 |