diff --git a/x/logic/interpreter/registry.go b/x/logic/interpreter/registry.go
index e3e1bb06..6dfefb64 100644
--- a/x/logic/interpreter/registry.go
+++ b/x/logic/interpreter/registry.go
@@ -116,6 +116,7 @@ var Registry = map[string]RegistryEntry{
 	"bank_locked_balances/2":    {predicate.BankLockedBalances, 1},
 	"did_components/2":          {predicate.DIDComponents, 1},
 	"sha_hash/2":                {predicate.SHAHash, 1},
+	"hex_bytes/2":               {predicate.HexBytes, 1},
 }
 
 // RegistryNames is the list of the predicate names in the Registry.
diff --git a/x/logic/predicate/crypto.go b/x/logic/predicate/crypto.go
index ae6e0522..2a448c18 100644
--- a/x/logic/predicate/crypto.go
+++ b/x/logic/predicate/crypto.go
@@ -2,9 +2,11 @@ package predicate
 
 import (
 	"context"
+	"encoding/hex"
 	"fmt"
 
 	"github.com/ichiban/prolog/engine"
+	"github.com/okp4/okp4d/x/logic/util"
 	"github.com/tendermint/tendermint/crypto"
 )
 
@@ -20,3 +22,45 @@ func SHAHash(vm *engine.VM, data, hash engine.Term, cont engine.Cont, env *engin
 		}
 	})
 }
+
+func HexBytes(vm *engine.VM, hexa, bts engine.Term, cont engine.Cont, env *engine.Env) *engine.Promise {
+	return engine.Delay(func(ctx context.Context) *engine.Promise {
+		var result []byte
+
+		switch h := env.Resolve(hexa).(type) {
+		case engine.Variable:
+		case engine.Atom:
+			src := []byte(h.String())
+			result = make([]byte, hex.DecodedLen(len(src)))
+			_, err := hex.Decode(result, src)
+			if err != nil {
+				return engine.Error(fmt.Errorf("hex_bytes/2: failed decode hexadecimal %w", err))
+			}
+		default:
+			return engine.Error(fmt.Errorf("hex_bytes/2: invalid hex type: %T, should be Atom or Variable", h))
+		}
+
+		switch b := env.Resolve(bts).(type) {
+		case engine.Variable:
+			if result == nil {
+				return engine.Error(fmt.Errorf("hex_bytes/2: nil hexadecimal conversion in input"))
+			}
+			return engine.Unify(vm, bts, BytesToList(result), cont, env)
+		case engine.Compound:
+			if b.Arity() != 2 || b.Functor().String() != "." {
+				return engine.Error(fmt.Errorf("hex_bytes/2: bytes should be a List, give %T", b))
+			}
+			iter := engine.ListIterator{List: b, Env: env}
+
+			src, err := ListToBytes(iter, env)
+			if err != nil {
+				return engine.Error(fmt.Errorf("hex_bytes/2: failed convert list into bytes: %w", err))
+			}
+			dst := hex.EncodeToString(src)
+			return engine.Unify(vm, hexa, util.StringToTerm(dst), cont, env)
+		default:
+			return engine.Error(fmt.Errorf("hex_bytes/2: invalid hex type: %T, should be Variable or List", b))
+		}
+
+	})
+}
diff --git a/x/logic/predicate/util.go b/x/logic/predicate/util.go
index 4e29b985..eaab5591 100644
--- a/x/logic/predicate/util.go
+++ b/x/logic/predicate/util.go
@@ -68,10 +68,6 @@ func ListToBytes(terms engine.ListIterator, env *engine.Env) ([]byte, error) {
 		term := env.Resolve(terms.Current())
 		switch t := term.(type) {
 		case engine.Integer:
-			//b, ok :=
-			//if !ok {
-			//	return nil, fmt.Errorf("couldn't cast '%d' to byte", term)
-			//}
 			bt = append(bt, byte(t))
 		default:
 			return nil, fmt.Errorf("invalid term type in list %T, only integer allowed", term)