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enforce seed to be nil or 32 bytes

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This commit is contained in:
lehugueni
2024-11-11 12:14:43 +01:00
parent 312b447f4f
commit 43f73e6290
2 changed files with 26 additions and 17 deletions
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7
core/rlwe/keygenerator.go
View File

@@ -279,12 +279,13 @@ func (kgen KeyGenerator) genEvaluationKey(skIn ring.Poly, skOut ringqp.Poly, evk
// For a compressed evaluation key, a seed is created and stored in the EvaluationKey struct
// struct while an uncompressed key uses an ephemeral seed.
if evk.IsCompressed() {
evk.Seed = make([]byte, 32)
if n, err := kgen.prng.Read(evk.Seed); n != 32 || err != nil {
var seed [32]byte
if n, err := kgen.prng.Read(seed[:]); n != 32 || err != nil {
panic(fmt.Errorf("unable to sample evaluation key seed"))
}
evk.Seed = &seed
sampler, err := sampling.NewKeyedPRNG(evk.Seed)
sampler, err := sampling.NewKeyedPRNG(seed[:])
if err != nil {
panic(fmt.Errorf("sampling.NewKeyedPRNG: %w", err))
}

36
core/rlwe/keys.go
View File

@@ -292,7 +292,7 @@ func (p *PublicKey) isEncryptionKey() {}
// is used to bring it back to its original key.
type EvaluationKey struct {
GadgetCiphertext
Seed []byte
Seed *[32]byte // Must be != nil iff EvaluationKey.IsCompressed() = true
}
type EvaluationKeyParameters struct {
@@ -362,7 +362,11 @@ func (evk EvaluationKey) Expand(params ParameterProvider, buffer *GadgetCipherte
return fmt.Errorf("evaluation key is not compressed")
}
prng, err := sampling.NewKeyedPRNG(evk.Seed)
if evk.Seed == nil {
return fmt.Errorf("seed is missing")
}
prng, err := sampling.NewKeyedPRNG((*evk.Seed)[:])
if err != nil {
panic(fmt.Errorf("sampling.NewKeyedPRNG: %s", err))
}
@@ -419,7 +423,10 @@ func (evk EvaluationKey) Expand(params ParameterProvider, buffer *GadgetCipherte
// BinarySize returns the serialized size of the object in bytes.
func (evk EvaluationKey) BinarySize() (size int) {
return evk.GadgetCiphertext.BinarySize() + len(evk.Seed)
if evk.Seed != nil {
return evk.GadgetCiphertext.BinarySize() + len(*evk.Seed)
}
return evk.GadgetCiphertext.BinarySize()
}
// WriteTo writes the object on an [io.Writer]. It implements the [io.WriterTo]
@@ -446,13 +453,14 @@ func (evk EvaluationKey) WriteTo(w io.Writer) (n int64, err error) {
n += inc
if evk.IsCompressed() {
if inc, err = buffer.Write(w, evk.Seed); err != nil {
return n + inc, err
// Sanity check, should not happen unless evk has been manually modified
if evk.Seed == nil {
return n + inc, fmt.Errorf("writing compressed evaluation key: the seed is nil")
}
// Sanity check, should not happen unless the size of the seed has been modified in the code
if inc != 32 {
return n + inc, fmt.Errorf("writing compressed evaluation key: the size of the seed=%d != 32", inc)
if inc, err = buffer.Write(w, (*evk.Seed)[:]); err != nil {
return n + inc, err
}
n += inc
@@ -484,7 +492,6 @@ func (evk *EvaluationKey) ReadFrom(r io.Reader) (n int64, err error) {
case buffer.Reader:
var inc int64
var incInt int
if inc, err = evk.GadgetCiphertext.ReadFrom(r); err != nil {
return n + inc, err
@@ -493,13 +500,14 @@ func (evk *EvaluationKey) ReadFrom(r io.Reader) (n int64, err error) {
n += inc
if evk.IsCompressed() {
seed := make([]byte, 32)
if incInt, err = r.Read(seed); err != nil {
return n + int64(incInt), err
var seed [32]byte
if inc, err = buffer.Read(r, seed[:]); err != nil {
return n + inc, err
}
evk.Seed = seed
n += int64(incInt)
evk.Seed = &seed
n += inc
}
return