diff --git a/Cargo.lock b/Cargo.lock
index f38102e..71697cf 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1755,6 +1755,8 @@ dependencies = [
  "dirs",
  "emojis",
  "futures-channel",
+ "hex",
+ "hex-literal",
  "hostname",
  "image",
  "insta",
@@ -1779,6 +1781,7 @@ dependencies = [
  "scopeguard",
  "serde",
  "serde_json",
+ "sha2",
  "sqlx",
  "tempfile",
  "textwrap",
@@ -1897,6 +1900,12 @@ version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
+[[package]]
+name = "hex-literal"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6fe2267d4ed49bc07b63801559be28c718ea06c4738b7a03c94df7386d2cde46"
+
 [[package]]
 name = "hkdf"
 version = "0.12.4"
@@ -3141,7 +3150,7 @@ checksum = "94e851c7654eed9e68d7d27164c454961a616cf8c203d500607ef22c737b51bb"
 [[package]]
 name = "presage"
 version = "0.6.0-dev"
-source = "git+https://github.com/whisperfish/presage?rev=2d9a02b#2d9a02b9f5534e2d79811be62ed70a64c75215c8"
+source = "git+https://github.com/whisperfish/presage?rev=6d7003f#6d7003fed1fa0397d42ac257ed49573d01ca6e93"
 dependencies = [
  "base64 0.21.5",
  "futures",
@@ -3152,6 +3161,7 @@ dependencies = [
  "rand",
  "serde",
  "serde_json",
+ "sha2",
  "thiserror",
  "tokio",
  "url",
@@ -3160,7 +3170,7 @@ dependencies = [
 [[package]]
 name = "presage-store-cipher"
 version = "0.1.0"
-source = "git+https://github.com/whisperfish/presage?rev=2d9a02b#2d9a02b9f5534e2d79811be62ed70a64c75215c8"
+source = "git+https://github.com/whisperfish/presage?rev=6d7003f#6d7003fed1fa0397d42ac257ed49573d01ca6e93"
 dependencies = [
  "blake3",
  "chacha20poly1305",
@@ -3177,7 +3187,7 @@ dependencies = [
 [[package]]
 name = "presage-store-sled"
 version = "0.6.0-dev"
-source = "git+https://github.com/whisperfish/presage?rev=2d9a02b#2d9a02b9f5534e2d79811be62ed70a64c75215c8"
+source = "git+https://github.com/whisperfish/presage?rev=6d7003f#6d7003fed1fa0397d42ac257ed49573d01ca6e93"
 dependencies = [
  "async-trait",
  "base64 0.12.3",
diff --git a/Cargo.toml b/Cargo.toml
index 44cf05f..3e66432 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -28,58 +28,61 @@ debug = true
 dev = ["prost", "base64"]
 
 [dependencies]
-presage = { git = "https://github.com/whisperfish/presage", rev = "2d9a02b" }
-presage-store-sled = { git = "https://github.com/whisperfish/presage", rev = "2d9a02b" }
+presage = { git = "https://github.com/whisperfish/presage", rev = "6d7003f" }
+presage-store-sled = { git = "https://github.com/whisperfish/presage", rev = "6d7003f" }
 
+# dev feature dependencies
+prost = { version = "0.10.4", optional = true }
+base64 = { version = "0.13.1", optional = true }
+
+aho-corasick = "0.7.19"
 anyhow = "1.0.66"
+arboard = { version = "3.2.0", features = ["wayland-data-control"] }
 async-trait = "0.1.58"
 chrono = { version = "0.4.22", default-features = false, features = ["serde"] }
+clap = { version = "4.0.19", features = ["derive"] }
 crossterm = { version = "0.27.0", features = ["event-stream"] }
 derivative = "2.2.0"
 dirs = "4.0.0"
+emojis = "0.6.1"
+futures-channel = "0.3.25"
+hex = "0.4.3"
 hostname = "0.3.1"
 image = { version = "0.24.6", default-features = false, features = ["png"] }
 itertools = "0.10.5"
 log-panics = "2.1.0"
 mime_guess = "2.0.4"
 notify-rust = "4.5.10"
+once_cell = "1.18.0"
 opener = "0.5.0"
 phonenumber = "0.3.1"
+postcard = { version = "1.0.4", features = ["alloc"] }
+qr2term = { git = "https://github.com/boxdot/qr2term-rs", rev = "ed8ae7f" }
+ratatui = "0.23.0"
+rayon = "1.7.0"
+regex = "1.9.5"
 regex-automata = "0.1.10"
 scopeguard = "1.1.0"
 serde = { version = "1.0.147", features = ["derive"] }
 serde_json = "1.0.87"
+sha2 = "0.10.8"
+sqlx = { version = "0.7.2", features = ["sqlite", "runtime-tokio-rustls", "uuid", "chrono"] }
 textwrap = "0.16.0"
+thiserror = "1.0.40"
+thread_local = "1.1.7"
 tokio = { version = "1.21.2", default-features = false, features = ["rt-multi-thread", "macros", "net", "time"] }
 tokio-stream = "0.1.11"
 toml = "0.5.9"
-unicode-width = "0.1.10"
-uuid = { version = "1.2", features = ["v4"] }
-whoami = "1.2.3"
 tracing = "0.1.37"
 tracing-appender = "0.2.2"
 tracing-subscriber = "0.3.16"
-futures-channel = "0.3.25"
-qr2term = { git = "https://github.com/boxdot/qr2term-rs", rev = "ed8ae7f" }
-clap = { version = "4.0.19", features = ["derive"] }
-aho-corasick = "0.7.19"
-sqlx = { version = "0.7.2", features = ["sqlite", "runtime-tokio-rustls", "uuid", "chrono"] }
-thiserror = "1.0.40"
-postcard = { version = "1.0.4", features = ["alloc"] }
-emojis = "0.6.1"
-
-# dev feature dependencies
-prost = { version = "0.10.4", optional = true }
-base64 = { version = "0.13.1", optional = true }
-arboard = { version = "3.2.0", features = ["wayland-data-control"] }
-rayon = "1.7.0"
-thread_local = "1.1.7"
-ratatui = "0.23.0"
-regex = "1.9.5"
-once_cell = "1.18.0"
+unicode-width = "0.1.10"
+uuid = { version = "1.2", features = ["v4"] }
+whoami = "1.2.3"
 
 [dev-dependencies]
 criterion = { version = "0.5", features = ["async_tokio", "html_reports"] }
+hex-literal = "0.4.1"
 insta = { version = "1.21.0", features = ["json"] }
 quickcheck = "1.0.3"
 quickcheck_macros = "1.0.0"
@@ -89,7 +92,7 @@ tempfile = "3.3.0"
 name = "app"
 harness = false
 
-# [patch."https://github.com/whisperfish/presage.git"]
+[patch."https://github.com/whisperfish/presage.git"]
 # presage = { path = "../presage/presage" }
 # presage-store-sled = { path = "../presage/presage-store-sled" }
 #
diff --git a/src/signal/attachment.rs b/src/signal/attachment.rs
new file mode 100644
index 0000000..0139bc3
--- /dev/null
+++ b/src/signal/attachment.rs
@@ -0,0 +1,204 @@
+use std::path::{Path, PathBuf};
+
+use anyhow::Context;
+use chrono::Local;
+use mime_guess::mime::{APPLICATION_OCTET_STREAM, IMAGE_JPEG};
+use mime_guess::{get_mime_extensions, Mime};
+use presage::proto::AttachmentPointer;
+use tracing::info;
+
+use crate::signal::Attachment;
+use crate::util::utc_timestamp_msec_to_local;
+
+const DIGEST_BYTES_LEN: usize = 4;
+
+pub(super) fn save(
+    data_dir: impl AsRef<Path>,
+    pointer: AttachmentPointer,
+    data: Vec<u8>,
+) -> anyhow::Result<Attachment> {
+    let base_dir = data_dir.as_ref().join("files");
+
+    let digest = pointer
+        .digest
+        .as_deref()
+        .context("dropping attachment without digest")?;
+    let digest_hex = hex::encode(digest);
+
+    let mime: Mime = pointer
+        .content_type()
+        .parse()
+        .unwrap_or(APPLICATION_OCTET_STREAM);
+
+    let name = derive_name(&pointer, digest, &mime);
+
+    let date = pointer
+        .upload_timestamp
+        .map(utc_timestamp_msec_to_local)
+        .unwrap_or_else(Local::now)
+        .date_naive();
+    let filedir = base_dir.join(date.to_string());
+    let filepath = conflict_free_filename(&filedir, name);
+
+    std::fs::create_dir_all(&filedir)
+        .with_context(|| format!("failed to create dir: {}", filedir.display()))?;
+    std::fs::write(&filepath, data)
+        .with_context(|| format!("failed to save attachment at: {}", filepath.display()))?;
+
+    info!(dest =% filepath.display(), "saved attachment");
+
+    Ok(Attachment {
+        id: digest_hex,
+        content_type: mime.to_string(),
+        filename: filepath,
+        size: pointer.size.unwrap_or_default(),
+    })
+}
+
+fn conflict_free_filename(filedir: &Path, name: String) -> PathBuf {
+    let mut filepath = filedir.join(&name);
+
+    // resolve conflicts
+    let mut idx = 0;
+    while filepath.exists() {
+        let name_path = Path::new(&name);
+        match name_path.file_stem().zip(name_path.extension()) {
+            Some((stem, extension)) => {
+                idx += 1;
+                let stem = stem.to_string_lossy();
+                let extension = extension.to_string_lossy();
+                filepath = filedir.join(format!("{stem}.{idx}.{extension}"));
+            }
+            None => {
+                idx += 1;
+                filepath = filedir.join(format!("{name}.{idx}"));
+            }
+        }
+    }
+    filepath
+}
+
+fn derive_name(pointer: &AttachmentPointer, digest: &[u8], mime: &Mime) -> String {
+    pointer.file_name.clone().unwrap_or_else(|| {
+        let mut name = hex::encode(&digest[..DIGEST_BYTES_LEN]);
+        let extension = if mime == &IMAGE_JPEG {
+            // special case due to: <https://github.com/abonander/mime_guess/issues/59>
+            Some("jpeg")
+        } else if mime == &APPLICATION_OCTET_STREAM {
+            None
+        } else {
+            get_mime_extensions(mime).and_then(|extensions| extensions.first().copied())
+        };
+        if let Some(extension) = extension {
+            name.push('.');
+            name.push_str(extension);
+        };
+        name
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use hex_literal::hex;
+
+    use super::*;
+
+    fn attachment_pointer(
+        content_type: &str,
+        digest: &[u8],
+        file_name: Option<&str>,
+        upload_timestamp: u64,
+    ) -> AttachmentPointer {
+        AttachmentPointer {
+            content_type: Some(content_type.into()),
+            digest: Some(digest.into()),
+            file_name: file_name.map(|s| s.to_owned()),
+            upload_timestamp: Some(upload_timestamp),
+            key: None,
+            size: Some(42),
+            thumbnail: None,
+            incremental_digest: None,
+            incremental_mac_chunk_size: None,
+            flags: None,
+            width: None,
+            height: None,
+            caption: None,
+            blur_hash: None,
+            cdn_number: None,
+            attachment_identifier: None,
+        }
+    }
+
+    #[test]
+    fn test_save() {
+        let tempdir = tempfile::tempdir().unwrap();
+
+        let digest = hex!("d51e9a355d4351ae5fbf2846d18bb384471555aa0ea6ee9075eb63f99ecddf77");
+        let upload_timestamp = 1703160458 * 1000;
+
+        let attachment = save(
+            tempdir.path(),
+            attachment_pointer("image/jpeg", &digest, Some("image.jpeg"), upload_timestamp),
+            vec![42],
+        )
+        .unwrap();
+
+        assert_eq!(attachment.id, hex::encode(digest));
+        assert_eq!(attachment.content_type, "image/jpeg");
+        assert_eq!(attachment.size, 42);
+        assert_eq!(
+            attachment.filename,
+            tempdir.path().join("files/2023-12-21/image.jpeg")
+        );
+
+        assert_eq!(std::fs::read(attachment.filename).unwrap(), &[42]);
+
+        // duplicate
+        let attachment = save(
+            tempdir.path(),
+            attachment_pointer("image/jpeg", &digest, Some("image.jpeg"), upload_timestamp),
+            vec![42],
+        )
+        .unwrap();
+        assert_eq!(
+            attachment.filename,
+            tempdir.path().join("files/2023-12-21/image.1.jpeg")
+        );
+
+        // without name
+        let attachment = save(
+            tempdir.path(),
+            attachment_pointer("image/jpeg", &digest, None, upload_timestamp),
+            vec![42],
+        )
+        .unwrap();
+        assert_eq!(
+            attachment.filename,
+            tempdir.path().join("files/2023-12-21/d51e9a35.jpeg")
+        );
+
+        // without name and mime octet-stream
+        let attachment = save(
+            tempdir.path(),
+            attachment_pointer("application/octet-stream", &digest, None, upload_timestamp),
+            vec![42],
+        )
+        .unwrap();
+        assert_eq!(
+            attachment.filename,
+            tempdir.path().join("files/2023-12-21/d51e9a35")
+        );
+
+        // without name and mime pdf
+        let attachment = save(
+            tempdir.path(),
+            attachment_pointer("application/pdf", &digest, None, upload_timestamp),
+            vec![42],
+        )
+        .unwrap();
+        assert_eq!(
+            attachment.filename,
+            tempdir.path().join("files/2023-12-21/d51e9a35.pdf")
+        );
+    }
+}
diff --git a/src/signal/impl.rs b/src/signal/impl.rs
index ea73b1f..02fa8ae 100644
--- a/src/signal/impl.rs
+++ b/src/signal/impl.rs
@@ -2,9 +2,8 @@
 
 use std::pin::Pin;
 
-use anyhow::{anyhow, Context};
+use anyhow::Context;
 use async_trait::async_trait;
-use chrono::Utc;
 use presage::libsignal_service::content::{Content, ContentBody};
 use presage::libsignal_service::models::Contact;
 use presage::libsignal_service::prelude::{Group, ProfileKey};
@@ -16,14 +15,16 @@ use presage::store::ContentsStore;
 use presage_store_sled::SledStore;
 use tokio::sync::oneshot;
 use tokio_stream::Stream;
-use tracing::{error, warn};
+use tracing::error;
 use uuid::Uuid;
 
 use crate::data::{Channel, ChannelId, GroupData, Message};
 use crate::receipt::Receipt;
 use crate::util::utc_now_timestamp_msec;
 
-use super::{Attachment, GroupMasterKeyBytes, ProfileKeyBytes, ResolvedGroup, SignalManager};
+use super::{
+    attachment, Attachment, GroupMasterKeyBytes, ProfileKeyBytes, ResolvedGroup, SignalManager,
+};
 
 pub(super) struct PresageManager {
     manager: presage::Manager<SledStore, Registered>,
@@ -80,36 +81,11 @@ impl SignalManager for PresageManager {
         &mut self,
         attachment_pointer: AttachmentPointer,
     ) -> anyhow::Result<Attachment> {
+        let attachment_data = self.manager.get_attachment(&attachment_pointer).await?;
         let data_dir = dirs::data_dir()
-            .ok_or_else(|| anyhow!("could not find data directory"))?
+            .context("could not find data directory")?
             .join("gurk");
-        let attachment_data = self.manager.get_attachment(&attachment_pointer).await?;
-
-        let date = Utc::now().to_rfc3339();
-        let filename = match attachment_pointer.content_type.as_deref() {
-            Some("image/jpeg") => format!("signal-{date}.jpg"),
-            Some("image/gif") => format!("signal-{date}.gif"),
-            Some("image/png") => format!("signal-{date}.png"),
-            Some(mimetype) => {
-                warn!("unsupported attachment mimetype: {}", mimetype);
-                format!("signal-{date}")
-            }
-            None => {
-                format!("signal-{date}")
-            }
-        };
-
-        let filepath = data_dir.join(filename);
-        std::fs::write(&filepath, attachment_data)?;
-
-        Ok(Attachment {
-            id: date,
-            content_type: attachment_pointer
-                .content_type
-                .unwrap_or_else(|| "application/octet-stream".to_owned()),
-            filename: filepath,
-            size: attachment_pointer.size.unwrap_or_default(),
-        })
+        attachment::save(data_dir, attachment_pointer, attachment_data)
     }
 
     fn send_receipt(&self, sender_uuid: Uuid, timestamps: Vec<u64>, receipt: Receipt) {
diff --git a/src/signal/mod.rs b/src/signal/mod.rs
index c752480..da63715 100644
--- a/src/signal/mod.rs
+++ b/src/signal/mod.rs
@@ -1,3 +1,4 @@
+mod attachment;
 mod r#impl;
 mod manager;
 pub mod test;