diff --git a/sckutils/sckutils.go b/sckutils/sckutils.go
index 3d238d7..7c4ef08 100644
--- a/sckutils/sckutils.go
+++ b/sckutils/sckutils.go
@@ -9,13 +9,26 @@
 // and operations.
 package sckutils
 
-// DataBuffer represents a generic data buffer for smart card operations.
-type DataBuffer struct {
-	Data []byte
-}
+import (
+	"fmt"
+	"strings"
+)
 
 // ConvertToHexString converts a byte slice to a hex string.
-func ConvertToHexString(data []byte) string { return "" }
+func ConvertToHexString(data []byte) string {
+	const f = "%02X" // Define the format specifier
+	var b strings.Builder
+
+	// Write each byte in hex format to the builder
+	for i, v := range data {
+		if i > 0 {
+			b.WriteString(":") // Add a colon before each byte except the first one
+		}
+		b.WriteString(fmt.Sprintf(f, v))
+	}
+
+	return b.String()
+}
 
 // ParseHexString parses a hex string into a byte slice.
 func ParseHexString(hexStr string) ([]byte, error) { return nil, nil }
@@ -26,8 +39,35 @@ func CheckStatusCode(code byte) bool { return false }
 // NewDataBuffer creates a new DataBuffer with the provided data.
 func NewDataBuffer(data []byte) *DataBuffer { return nil }
 
-// Marshal serializes a DataBuffer into a byte slice.
-func (db *DataBuffer) Marshal() ([]byte, error) { return nil, nil }
-
 // UnmarshalDataBuffer sets the DataBuffer fields from a byte slice.
 func UnmarshalDataBuffer(data []byte) (*DataBuffer, error) { return nil, nil }
+
+// HumanizeBytes converts a size in bytes to a human-readable string in KB, MB, GB, etc.
+func HumanizeBytes(bytes int64) string {
+	const (
+		kB int64 = 1 << 10 // 1024
+		mB int64 = 1 << 20 // 1048576
+		gB int64 = 1 << 30 // 1073741824
+	)
+
+	format := "%.2f %s"
+	switch {
+	case bytes < kB:
+		return fmt.Sprintf("%d B", bytes)
+	case bytes < mB:
+		return fmt.Sprintf(format, float64(bytes)/float64(kB), "KB")
+	case bytes < gB:
+		return fmt.Sprintf(format, float64(bytes)/float64(mB), "MB")
+	default:
+		// When file size is larger than 1 MB
+		return fmt.Sprintf(format, float64(bytes)/float64(gB), "GB")
+	}
+}
+
+// DataBuffer represents a generic data buffer for smart card operations.
+type DataBuffer struct {
+	Data []byte
+}
+
+// Marshal serializes a DataBuffer into a byte slice.
+func (db *DataBuffer) Marshal() ([]byte, error) { return nil, nil }
diff --git a/sckutils/sckutils_test.go b/sckutils/sckutils_test.go
new file mode 100644
index 0000000..3505389
--- /dev/null
+++ b/sckutils/sckutils_test.go
@@ -0,0 +1,52 @@
+// Copyright 2023 The Happy Authors
+// Licensed under the Apache License, Version 2.0.
+// See the LICENSE file.
+
+package sckutils
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestFormatByteSlice(t *testing.T) {
+	// Test case 1: An empty byte slice should return an empty string.
+	emptySlice := []byte{}
+	result := ConvertToHexString(emptySlice)
+	expected := ""
+	if result != expected {
+		t.Errorf("Expected '%s', but got '%s'", expected, result)
+	}
+
+	// Test case 2: A byte slice with some data should be formatted as expected.
+	dataSlice := []byte{72, 101, 108, 108, 111} // ASCII values for "Hello"
+	result = ConvertToHexString(dataSlice)
+	expected = "48:65:6C:6C:6F" // Hexadecimal representation of ASCII values
+	if result != expected {
+		t.Errorf("Expected '%s', but got '%s'", expected, result)
+	}
+}
+
+func TestHumanizeBytes(t *testing.T) {
+	tests := []struct {
+		bytes    int64
+		expected string
+	}{
+		{500, "500 B"},
+		{1024, "1.00 KB"},
+		{1536, "1.50 KB"},
+		{1048576, "1.00 MB"},
+		{1572864, "1.50 MB"},
+		{1073741824, "1.00 GB"},
+		{1610612736, "1.50 GB"},
+	}
+
+	for _, test := range tests {
+		t.Run(fmt.Sprintf("%dBytes", test.bytes), func(t *testing.T) {
+			result := HumanizeBytes(test.bytes)
+			if result != test.expected {
+				t.Errorf("HumanizeBytes(%d) = %s; want %s", test.bytes, result, test.expected)
+			}
+		})
+	}
+}