[utils/sampling]: removed panics & removed PRNG in ckks.Encoder

ckks/encoder.go

@@ -11,7 +11,6 @@ import (
 	"github.com/tuneinsight/lattigo/v4/rlwe/ringqp"
 	"github.com/tuneinsight/lattigo/v4/utils"
 	"github.com/tuneinsight/lattigo/v4/utils/bignum"
-	"github.com/tuneinsight/lattigo/v4/utils/sampling"
 )
 
 type Float interface {
@@ -62,8 +61,6 @@ type Encoder struct {
 	m            int
 	rotGroup     []int
 
-	prng sampling.PRNG
-
 	roots     interface{}
 	buffCmplx interface{}
 }
@@ -84,13 +81,6 @@ func NewEncoder(parameters Parameters, precision ...uint) (ecd *Encoder) {
 		fivePows &= (m - 1)
 	}
 
-	prng, err := sampling.NewPRNG()
-
-	// This error should never happen.
-	if err != nil {
-		panic(err)
-	}
-
 	var prec uint
 	if len(precision) != 0 && precision[0] != 0 {
 		prec = precision[0]
@@ -106,7 +96,6 @@ func NewEncoder(parameters Parameters, precision ...uint) (ecd *Encoder) {
 		buff:         parameters.RingQ().NewPoly(),
 		m:            m,
 		rotGroup:     rotGroup,
-		prng:         prng,
 	}
 
 	if prec <= 53 {
@@ -1183,13 +1172,6 @@ func (ecd *Encoder) polyToFloatNoCRT(coeffs []uint64, values FloatSlice, scale r
 // that can be used concurrently with the original object.
 func (ecd Encoder) ShallowCopy() *Encoder {
 
-	prng, err := sampling.NewPRNG()
-
-	// This error should never happen.
-	if err != nil {
-		panic(err)
-	}
-
 	var buffCmplx interface{}
 
 	if prec := ecd.prec; prec <= 53 {
@@ -1212,7 +1194,6 @@ func (ecd Encoder) ShallowCopy() *Encoder {
 		buff:         *ecd.buff.CopyNew(),
 		m:            ecd.m,
 		rotGroup:     ecd.rotGroup,
-		prng:         prng,
 		roots:        ecd.roots,
 		buffCmplx:    buffCmplx,
 	}

utils/sampling/prng.go

@@ -2,6 +2,7 @@ package sampling
 
 import (
 	"crypto/rand"
+	"fmt"
 	"io"
 
 	"golang.org/x/crypto/blake2b"
@@ -37,7 +38,7 @@ func NewPRNG() (*KeyedPRNG, error) {
 	prng := new(KeyedPRNG)
 	key := make([]byte, 64)
 	if _, err := rand.Read(key); err != nil {
-		panic("crypto rand error")
+		return fmt.Errorf("crypto rand error: %w", err)
 	}
 	prng.key = key
 	prng.xof, err = blake2b.NewXOF(blake2b.OutputLengthUnknown, key)
@@ -55,10 +56,7 @@ func (prng *KeyedPRNG) Key() (key []byte) {
 
 // Read reads bytes from the KeyedPRNG on sum.
 func (prng *KeyedPRNG) Read(sum []byte) (n int, err error) {
-	if n, err = prng.xof.Read(sum); err != nil {
-		panic(err)
-	}
-	return n, nil
+	return prng.xof.Read(sum)
 }
 
 // Reset resets the PRNG to its initial state.