@@ -30,7 +30,7 @@ import (
3030 "github.com/ethereum/go-ethereum/crypto/bn256"
3131 "github.com/ethereum/go-ethereum/params"
3232
33- //lint:ignore SA1019 Needed for precompile
33+ big2 "github.com/holiman/big"
3434 "golang.org/x/crypto/ripemd160"
3535)
3636
@@ -266,9 +266,10 @@ var (
266266// modexpMultComplexity implements bigModexp multComplexity formula, as defined in EIP-198
267267//
268268// def mult_complexity(x):
269- // if x <= 64: return x ** 2
270- // elif x <= 1024: return x ** 2 // 4 + 96 * x - 3072
271- // else: return x ** 2 // 16 + 480 * x - 199680
269+ //
270+ // if x <= 64: return x ** 2
271+ // elif x <= 1024: return x ** 2 // 4 + 96 * x - 3072
272+ // else: return x ** 2 // 16 + 480 * x - 199680
272273//
273274// where is x is max(length_of_MODULUS, length_of_BASE)
274275func modexpMultComplexity (x * big.Int ) * big.Int {
@@ -379,15 +380,24 @@ func (c *bigModExp) Run(input []byte) ([]byte, error) {
379380 }
380381 // Retrieve the operands and execute the exponentiation
381382 var (
382- base = new (big.Int ).SetBytes (getData (input , 0 , baseLen ))
383- exp = new (big.Int ).SetBytes (getData (input , baseLen , expLen ))
384- mod = new (big.Int ).SetBytes (getData (input , baseLen + expLen , modLen ))
383+ base = new (big2.Int ).SetBytes (getData (input , 0 , baseLen ))
384+ exp = new (big2.Int ).SetBytes (getData (input , baseLen , expLen ))
385+ mod = new (big2.Int ).SetBytes (getData (input , baseLen + expLen , modLen ))
386+ v []byte
385387 )
386- if mod .BitLen () == 0 {
388+
389+ switch {
390+ case mod .BitLen () == 0 :
387391 // Modulo 0 is undefined, return zero
388392 return common .LeftPadBytes ([]byte {}, int (modLen )), nil
393+ case base .BitLen () == 1 : // a bit length of 1 means it's 1 (or -1).
394+ //If base == 1, then we can just return base % mod (if mod >= 1, which it is)
395+ v = base .Mod (base , mod ).Bytes ()
396+ default :
397+ v = base .Exp (base , exp , mod ).Bytes ()
389398 }
390- return common .LeftPadBytes (base .Exp (base , exp , mod ).Bytes (), int (modLen )), nil
399+
400+ return common .LeftPadBytes (v , int (modLen )), nil
391401}
392402
393403// newCurvePoint unmarshals a binary blob into a bn256 elliptic curve point,
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