diff --git a/apk_frauder/src/extra_fields.rs b/apk_frauder/src/extra_fields.rs
new file mode 100644
index 0000000..6bc532d
--- /dev/null
+++ b/apk_frauder/src/extra_fields.rs
@@ -0,0 +1,139 @@
+use std::io::{Cursor, Write};
+
+use androscalpel_serializer::{ReadSeek, Result, Serializable};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ExtraField {
+    Zip64(Zip64ExtraField),
+    Generic(GenericExtraField),
+}
+
+impl ExtraField {
+    fn to_generic(&self) -> Result<GenericExtraField> {
+        match self {
+            Self::Zip64(field) => field.to_generic_field(),
+            Self::Generic(field) => Ok(field.clone()),
+        }
+    }
+}
+
+impl Serializable for ExtraField {
+    fn serialize(&self, output: &mut dyn Write) -> Result<()> {
+        self.to_generic()?.serialize(output)
+    }
+
+    fn deserialize(input: &mut dyn ReadSeek) -> Result<Self> {
+        Ok(Self::Generic(GenericExtraField::deserialize(input)?))
+
+        /*
+        match field.id {
+            Zip64ExtraField::ID => Ok(Self::Zip64(Zip64ExtraField::from_generic(&field)?)),
+            _ => Ok(Self::Generic(field)),
+        }
+        */
+    }
+
+    fn size(&self) -> usize {
+        self.to_generic().unwrap().size()
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Zip64ExtraField {
+    pub original_size: Option<u64>,
+    pub compressed_size: Option<u64>,
+    pub offset_header: Option<u64>,
+    pub disk_number: Option<u32>,
+}
+
+impl Zip64ExtraField {
+    pub const ID: u16 = 0x0001;
+    fn to_generic_field(&self) -> Result<GenericExtraField> {
+        let mut data = Cursor::new(Vec::<u8>::new());
+        if let Some(original_size) = self.original_size {
+            original_size.serialize(&mut data)?;
+        }
+        if let Some(compressed_size) = self.compressed_size {
+            compressed_size.serialize(&mut data)?;
+        }
+        if let Some(offset_header) = self.offset_header {
+            offset_header.serialize(&mut data)?;
+        }
+        if let Some(disk_number) = self.disk_number {
+            disk_number.serialize(&mut data)?;
+        }
+
+        Ok(GenericExtraField {
+            id: Self::ID,
+            data: data.into_inner(),
+        })
+    }
+
+    pub fn from_generic(
+        field: &GenericExtraField,
+        original_size: bool,
+        compressed_size: bool,
+        offset_header: bool,
+        disk_number: bool,
+    ) -> Result<Self> {
+        assert_eq!(field.id, Self::ID);
+        let mut data = Cursor::new(&field.data);
+        let original_size = if original_size {
+            Some(u64::deserialize(&mut data)?)
+        } else {
+            None
+        };
+        let compressed_size = if compressed_size {
+            Some(u64::deserialize(&mut data)?)
+        } else {
+            None
+        };
+        let offset_header = if offset_header {
+            Some(u64::deserialize(&mut data)?)
+        } else {
+            None
+        };
+        let disk_number = if disk_number {
+            Some(u32::deserialize(&mut data)?)
+        } else {
+            None
+        };
+        Ok(Self {
+            original_size,
+            compressed_size,
+            offset_header,
+            disk_number,
+        })
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct GenericExtraField {
+    pub id: u16,
+    pub data: Vec<u8>,
+}
+
+impl Serializable for GenericExtraField {
+    fn serialize(&self, output: &mut dyn Write) -> Result<()> {
+        self.id.serialize(output)?;
+        (self.data.len() as u16).serialize(output)?;
+        for c in &self.data {
+            c.serialize(output)?;
+        }
+        Ok(())
+    }
+
+    fn deserialize(input: &mut dyn ReadSeek) -> Result<Self> {
+        let id = u16::deserialize(input)?;
+        let data_size = u16::deserialize(input)?;
+        let mut data = vec![];
+        for _ in 0..data_size {
+            data.push(u8::deserialize(input)?);
+        }
+        Ok(Self { id, data })
+    }
+
+    fn size(&self) -> usize {
+        4 + self.data.len()
+    }
+}
diff --git a/apk_frauder/src/file_header.rs b/apk_frauder/src/file_header.rs
index 9872594..144a524 100644
--- a/apk_frauder/src/file_header.rs
+++ b/apk_frauder/src/file_header.rs
@@ -1,5 +1,6 @@
-use std::io::{Cursor, SeekFrom, Write};
+use std::io::{SeekFrom, Write};
 
+use crate::extra_fields::{ExtraField, GenericExtraField, Zip64ExtraField};
 use crate::{cp437, Signature};
 use androscalpel_serializer::{ReadSeek, Result, Serializable};
 
@@ -8,142 +9,6 @@ pub enum Encoding {
     UTF8,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum ExtraField {
-    Zip64(Zip64ExtraField),
-    Generic(GenericExtraField),
-}
-
-impl ExtraField {
-    fn to_generic(&self) -> Result<GenericExtraField> {
-        match self {
-            Self::Zip64(field) => field.to_generic_field(),
-            Self::Generic(field) => Ok(field.clone()),
-        }
-    }
-}
-
-impl Serializable for ExtraField {
-    fn serialize(&self, output: &mut dyn Write) -> Result<()> {
-        self.to_generic()?.serialize(output)
-    }
-
-    fn deserialize(input: &mut dyn ReadSeek) -> Result<Self> {
-        Ok(Self::Generic(GenericExtraField::deserialize(input)?))
-
-        /*
-        match field.id {
-            Zip64ExtraField::ID => Ok(Self::Zip64(Zip64ExtraField::from_generic(&field)?)),
-            _ => Ok(Self::Generic(field)),
-        }
-        */
-    }
-
-    fn size(&self) -> usize {
-        self.to_generic().unwrap().size()
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct Zip64ExtraField {
-    original_size: Option<u64>,
-    compressed_size: Option<u64>,
-    offset_header: Option<u64>,
-    disk_number: Option<u32>,
-}
-
-impl Zip64ExtraField {
-    const ID: u16 = 0x0001;
-    fn to_generic_field(&self) -> Result<GenericExtraField> {
-        let mut data = Cursor::new(Vec::<u8>::new());
-        if let Some(original_size) = self.original_size {
-            original_size.serialize(&mut data)?;
-        }
-        if let Some(compressed_size) = self.compressed_size {
-            compressed_size.serialize(&mut data)?;
-        }
-        if let Some(offset_header) = self.offset_header {
-            offset_header.serialize(&mut data)?;
-        }
-        if let Some(disk_number) = self.disk_number {
-            disk_number.serialize(&mut data)?;
-        }
-
-        Ok(GenericExtraField {
-            id: Self::ID,
-            data: data.into_inner(),
-        })
-    }
-
-    fn from_generic(
-        field: &GenericExtraField,
-        original_size: bool,
-        compressed_size: bool,
-        offset_header: bool,
-        disk_number: bool,
-    ) -> Result<Self> {
-        assert_eq!(field.id, Self::ID);
-        let mut data = Cursor::new(&field.data);
-        let original_size = if original_size {
-            Some(u64::deserialize(&mut data)?)
-        } else {
-            None
-        };
-        let compressed_size = if compressed_size {
-            Some(u64::deserialize(&mut data)?)
-        } else {
-            None
-        };
-        let offset_header = if offset_header {
-            Some(u64::deserialize(&mut data)?)
-        } else {
-            None
-        };
-        let disk_number = if disk_number {
-            Some(u32::deserialize(&mut data)?)
-        } else {
-            None
-        };
-        Ok(Self {
-            original_size,
-            compressed_size,
-            offset_header,
-            disk_number,
-        })
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct GenericExtraField {
-    pub id: u16,
-    pub data: Vec<u8>,
-}
-
-impl Serializable for GenericExtraField {
-    fn serialize(&self, output: &mut dyn Write) -> Result<()> {
-        self.id.serialize(output)?;
-        (self.data.len() as u16).serialize(output)?;
-        for c in &self.data {
-            c.serialize(output)?;
-        }
-        Ok(())
-    }
-
-    fn deserialize(input: &mut dyn ReadSeek) -> Result<Self> {
-        let id = u16::deserialize(input)?;
-        let data_size = u16::deserialize(input)?;
-        let mut data = vec![];
-        for _ in 0..data_size {
-            data.push(u8::deserialize(input)?);
-        }
-        Ok(Self { id, data })
-    }
-
-    fn size(&self) -> usize {
-        4 + self.data.len()
-    }
-}
-
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FileHeader {
     // signature: Signature(0x02014b50)
diff --git a/apk_frauder/src/lib.rs b/apk_frauder/src/lib.rs
index cf38037..0d11d58 100644
--- a/apk_frauder/src/lib.rs
+++ b/apk_frauder/src/lib.rs
@@ -5,6 +5,7 @@ use androscalpel_serializer::Serializable;
 pub mod apk_signing_block;
 mod cp437;
 pub mod end_of_central_directory;
+pub mod extra_fields;
 pub mod file_header;
 
 use apk_signing_block::*;