diff --git a/Cargo.toml b/Cargo.toml
index 85c0199..1e4265a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,6 +16,7 @@ rand = "0.8"
 serde = { version = "1", features = ["derive"] }
 serde_with = "3"
 serde_yaml = "0.9"
+sha2 = "0.10.8"
 strum = { version = "0.25", features = ["derive"] }
 textwrap = "0.16"
 thiserror = "1"
diff --git a/README.md b/README.md
index a15695a..557c6d1 100644
--- a/README.md
+++ b/README.md
@@ -132,6 +132,8 @@ hashicorp_kv | `X`                           | `X`
 
   (Con: will skip initialization vector reuse for unchanged value.)
 
+- `--ignore-mac` flag. Why?
+
 - [Integrated formatting configuration](https://github.com/getsops/sops#32json-and-json_binary-indentation)
 
 - [Integrated secrets publishing](https://github.com/getsops/sops#219using-the-publish-command)
diff --git a/crates/lib/Cargo.toml b/crates/lib/Cargo.toml
index 0f99034..00b3bb7 100644
--- a/crates/lib/Cargo.toml
+++ b/crates/lib/Cargo.toml
@@ -11,6 +11,8 @@ age-test-utils = ["age", "test-utils", "dep:indoc", "dep:textwrap"]
 yaml = ["dep:serde_yaml"]
 # Ciphers
 aes-gcm = ["dep:aes-gcm"]
+# Hashers
+sha2 = ["dep:sha2"]
 # Test utils
 test-utils = ["dep:pretty_assertions"]
 
@@ -39,5 +41,8 @@ serde_yaml = { workspace = true, optional = true }
 # AES_GCM
 aes-gcm = { workspace = true, optional = true }
 
+# SHA2
+sha2 = { workspace = true, optional = true }
+
 # TEST_UTILS
 pretty_assertions = { workspace = true, optional = true }
diff --git a/crates/lib/src/cryptography/hasher/mod.rs b/crates/lib/src/cryptography/hasher/mod.rs
new file mode 100644
index 0000000..a8d3b02
--- /dev/null
+++ b/crates/lib/src/cryptography/hasher/mod.rs
@@ -0,0 +1,42 @@
+pub use core::Hasher;
+mod core {
+    use generic_array::{ArrayLength, GenericArray};
+
+    pub trait Hasher {
+        type OutputSize: ArrayLength<u8>;
+
+        fn new() -> Self;
+
+        fn update(&mut self, input: impl AsRef<[u8]>);
+
+        fn finalize(self) -> GenericArray<u8, Self::OutputSize>;
+    }
+}
+
+#[cfg(feature = "sha2")]
+pub use sha512::SHA512;
+#[cfg(feature = "sha2")]
+mod sha512 {
+    use sha2::{digest::OutputSizeUser, Digest, Sha512};
+
+    use crate::*;
+
+    #[derive(Debug)]
+    pub struct SHA512(Sha512);
+
+    impl Hasher for SHA512 {
+        type OutputSize = <Sha512 as OutputSizeUser>::OutputSize;
+
+        fn new() -> Self {
+            Self(Sha512::new())
+        }
+
+        fn update(&mut self, input: impl AsRef<[u8]>) {
+            self.0.update(input)
+        }
+
+        fn finalize(self) -> generic_array::GenericArray<u8, Self::OutputSize> {
+            self.0.finalize()
+        }
+    }
+}
diff --git a/crates/lib/src/cryptography/mod.rs b/crates/lib/src/cryptography/mod.rs
index 822f6a2..7d16778 100644
--- a/crates/lib/src/cryptography/mod.rs
+++ b/crates/lib/src/cryptography/mod.rs
@@ -16,5 +16,8 @@ pub use encrypted_data::EncryptedData;
 mod cipher;
 pub use cipher::*;
 
+mod hasher;
+pub use hasher::*;
+
 mod integration;
 pub use integration::*;
diff --git a/crates/lib/src/rops_file/mac.rs b/crates/lib/src/rops_file/mac.rs
new file mode 100644
index 0000000..579cb36
--- /dev/null
+++ b/crates/lib/src/rops_file/mac.rs
@@ -0,0 +1,125 @@
+use std::ops::Add;
+
+use generic_array::{typenum::Sum, ArrayLength, GenericArray};
+
+use crate::*;
+
+const MAC_ENCRYPTED_ONLY_INIT_BYTES: [u8; 32] = [
+    0x8a, 0x3f, 0xd2, 0xad, 0x54, 0xce, 0x66, 0x52, 0x7b, 0x10, 0x34, 0xf3, 0xd1, 0x47, 0xbe, 0xb, 0xb, 0x97, 0x5b, 0x3b, 0xf4, 0x4f, 0x72,
+    0xc6, 0xfd, 0xad, 0xec, 0x81, 0x76, 0xf2, 0x7d, 0x69,
+];
+
+#[derive(Debug)]
+pub struct Mac<H: Hasher>(GenericArray<u8, Sum<H::OutputSize, H::OutputSize>>)
+where
+    H::OutputSize: Add<H::OutputSize>,
+    Sum<H::OutputSize, H::OutputSize>: ArrayLength<u8>;
+
+impl<H: Hasher> Mac<H>
+where
+    H::OutputSize: Add<H::OutputSize>,
+    Sum<H::OutputSize, H::OutputSize>: ArrayLength<u8>,
+{
+    pub fn compute(from_encrypted_values_only: bool, decrypted_map: &RopsMap<Decrypted>) -> Self {
+        let mut hasher = H::new();
+        if from_encrypted_values_only {
+            hasher.update(MAC_ENCRYPTED_ONLY_INIT_BYTES);
+        }
+
+        traverse_map(&mut hasher, from_encrypted_values_only, decrypted_map);
+
+        // IMPROVEMENT: would be nice if the heap allocation could be avoided.
+        return Mac(GenericArray::from_iter(format!("{:X}", hasher.finalize()).into_bytes()));
+
+        fn traverse_map<Ha: Hasher>(hasher: &mut Ha, hash_encrypted_values_only: bool, map: &RopsMap<Decrypted>) {
+            traverse_map_recursive(hasher, hash_encrypted_values_only, map);
+
+            fn traverse_map_recursive<H: Hasher>(hasher: &mut H, hash_encrypted_values_only: bool, map: &RopsMap<Decrypted>) {
+                for (_, tree) in map.iter() {
+                    traverse_tree_recursive(hasher, hash_encrypted_values_only, tree)
+                }
+            }
+
+            fn traverse_tree_recursive<H: Hasher>(hasher: &mut H, hash_encrypted_values_only: bool, tree: &RopsTree<Decrypted>) {
+                match tree {
+                    RopsTree::Sequence(sequence) => sequence
+                        .iter()
+                        .for_each(|sub_tree| traverse_tree_recursive(hasher, hash_encrypted_values_only, sub_tree)),
+                    RopsTree::Map(map) => traverse_map_recursive(hasher, hash_encrypted_values_only, map),
+                    RopsTree::Null => (),
+                    RopsTree::Leaf(value) => {
+                        // TODO: use hash_encrypted_only once partial encryption is added
+                        hasher.update(value.as_bytes())
+                    }
+                }
+            }
+        }
+    }
+
+    pub fn encrypt<C: Cipher>(
+        self,
+        data_key: &DataKey,
+        last_modified_date_time: &LastModifiedDateTime,
+    ) -> Result<EncryptedRopsValue<C>, C::Error> {
+        let mut in_place_buffer = self.0;
+        let nonce = Nonce::new();
+        let authorization_tag = C::encrypt(
+            &nonce,
+            data_key,
+            in_place_buffer.as_mut_slice(),
+            last_modified_date_time.as_ref().to_rfc3339().as_bytes(),
+        )?;
+
+        Ok(EncryptedRopsValue {
+            data: in_place_buffer.to_vec().into(),
+            authorization_tag,
+            nonce,
+            value_variant: RopsValueVariant::String,
+        })
+    }
+}
+
+// WORKAROUND: derive proc macro struggles with trait bounds
+impl<H: Hasher> PartialEq for Mac<H>
+where
+    H::OutputSize: Add<H::OutputSize>,
+    Sum<H::OutputSize, H::OutputSize>: ArrayLength<u8>,
+{
+    fn eq(&self, other: &Self) -> bool {
+        self.0 == other.0
+    }
+}
+
+#[cfg(feature = "test-utils")]
+mod mock {
+    use super::*;
+
+    #[cfg(feature = "sha2")]
+    mod sha2 {
+        use super::*;
+
+        impl<H: Hasher> MockTestUtil for Mac<H>
+        where
+            H::OutputSize: Add<H::OutputSize>,
+            Sum<H::OutputSize, H::OutputSize>: ArrayLength<u8>,
+        {
+            fn mock() -> Self {
+                Self(GenericArray::from_slice(b"A0FBBFF515AC1EF88827C911653675DE4155901880355C59BA4FE4043395A0DE5EA77762EB3CAC54CC6F2B37EDDD916127A32566E810B0A5DADFA2F60B061331").to_owned())
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[cfg(feature = "sha2")]
+    mod sha2 {
+
+        use crate::*;
+
+        #[test]
+        fn computes_mac() {
+            assert_eq!(Mac::mock(), Mac::<SHA512>::compute(false, &RopsMap::mock()))
+        }
+    }
+}
diff --git a/crates/lib/src/rops_file/metadata/last_modified.rs b/crates/lib/src/rops_file/metadata/last_modified.rs
index 40c1bb0..f56ad32 100644
--- a/crates/lib/src/rops_file/metadata/last_modified.rs
+++ b/crates/lib/src/rops_file/metadata/last_modified.rs
@@ -1,9 +1,10 @@
 use std::fmt::Display;
 
 use chrono::{DateTime, Utc};
+use derive_more::AsRef;
 use serde::{Deserialize, Serialize};
 
-#[derive(Debug, PartialEq, Serialize, Deserialize)]
+#[derive(Debug, PartialEq, Serialize, Deserialize, AsRef)]
 pub struct LastModifiedDateTime(DateTime<Utc>);
 
 impl LastModifiedDateTime {
diff --git a/crates/lib/src/rops_file/mod.rs b/crates/lib/src/rops_file/mod.rs
index 3557289..e5a4d20 100644
--- a/crates/lib/src/rops_file/mod.rs
+++ b/crates/lib/src/rops_file/mod.rs
@@ -18,3 +18,6 @@ pub use state::{Decrypted, Encrypted, RopsFileState};
 
 mod format;
 pub use format::*;
+
+mod mac;
+pub use mac::Mac;