diff --git a/src/crypt.rs b/src/crypt.rs
index b952827..69ca75f 100644
--- a/src/crypt.rs
+++ b/src/crypt.rs
@@ -4,8 +4,16 @@ use crate::proto::{
     self,
     ser_de::{proto_enum, proto_struct, Value},
 };
-
+use hkdf::{hmac::Hmac, HmacImpl};
 use ring::aead::{self, Nonce};
+pub use seq::{SeqId, SeqIdGen};
+use sha2::digest::{
+    core_api::{self, CoreProxy},
+    generic_array::ArrayLength,
+    typenum::Unsigned,
+    OutputSizeUser,
+};
+use x25519_dalek::SharedSecret;
 
 pub struct TlsCiphertext {
     /// The encrypted [`TlsInnerPlaintext`] record.
@@ -19,37 +27,185 @@ impl From<Vec<u8>> for TlsCiphertext {
     }
 }
 
-pub fn compute_keys(shared_secret: SharedSecret) {
-    let hkdf_expand_label = |secret: &[u8], label: &[u8], context: &[u8], length| {
-        proto_struct! {
-            #[derive(Debug)]
-            pub struct HkdfLabel {
-                pub length: u16,
-                pub label: proto::ser_de::List<u8,u8>,
-                pub context: proto::ser_de::List<u8,u8>,
-            }
+trait HkdfHasher: OutputSizeUser {
+    const ZEROED: &'static [u8];
+    fn expand(ikm: &[u8], label: &[u8], okm: &mut [u8]) -> Result<(), hkdf::InvalidLength>;
+    fn extract(salt: &[u8], ikm: &[u8]) -> Vec<u8>;
+}
+macro_rules! impl_hkdf_hasher {
+    () => {
+        const ZEROED: &'static [u8] =
+            &[0; <<Self as OutputSizeUser>::OutputSize as Unsigned>::USIZE];
+        fn expand(ikm: &[u8], label: &[u8], okm: &mut [u8]) -> Result<(), hkdf::InvalidLength> {
+            hkdf::Hkdf::<Self>::new(None, ikm).expand(&label, okm)
         }
-        let mut hkdf_label = Vec::new();
-        HkdfLabel {
-            length,
-            label: {
-                let mut v = b"tls13 ".to_vec();
-                v.extend_from_slice(label);
-                v.into()
-            },
-            context: context.to_vec().into(),
+        fn extract(salt: &[u8], ikm: &[u8]) -> Vec<u8> {
+            hkdf::Hkdf::<Self>::extract(Some(&[]), &[])
+                .0
+                .as_slice()
+                .to_vec()
         }
-        .write(&mut hkdf_label)
-        .unwrap();
+    };
+}
+impl HkdfHasher for sha2::Sha256 {
+    impl_hkdf_hasher!();
+}
+impl HkdfHasher for sha2::Sha384 {
+    impl_hkdf_hasher!();
+}
 
-        // TODO: use correct algo, the cipher suite hash algorithm!
-        let mut okm = [0u8; 42];
-        hkdf::Hkdf::<sha2::Sha256>::new(None, secret).expand(&hkdf_label, &mut okm)
+// Key Schedule
+// https://datatracker.ietf.org/doc/html/rfc8446#section-7.1
+
+// The Hash function used by Transcript-Hash and HKDF is the cipher suite hash algorithm
+fn hkdf_expand_label<H: HkdfHasher>(secret: &[u8], label: &[u8], context: &[u8]) -> Vec<u8> {
+    proto_struct! {
+        #[derive(Debug)]
+        pub struct HkdfLabel {
+            pub length: u16,
+            pub label: proto::ser_de::List<u8, u8>,
+            pub context: proto::ser_de::List<u8, u8>,
+        }
+    }
+    let mut hkdf_label = Vec::new();
+    HkdfLabel {
+        // Hash.length is its output length in bytes
+        length: H::output_size().try_into().unwrap(),
+        label: {
+            let mut v = b"tls13 ".to_vec();
+            v.extend_from_slice(label);
+            v.into()
+        },
+        context: context.to_vec().into(),
+    }
+    .write(&mut hkdf_label)
+    .unwrap();
+
+    let mut okm = [0u8; 128];
+    H::expand(secret, &hkdf_label, &mut okm).unwrap();
+    okm[..H::output_size()].to_vec()
+}
+
+/// Messages is the concatenation of the indicated handshake messages,
+/// including the handshake message type and length fields, but not
+/// including record layer headers.
+fn derive_secret<H: HkdfHasher>(secret: &[u8], label: &[u8], messages: ()) -> Vec<u8> {
+    hkdf_expand_label::<H>(secret, label, &[])
+}
+
+pub struct CryptoProvider {
+    zeroed_of_hash_size: &'static [u8],
+    hkdf_extract: fn(salt: &[u8], ikm: &[u8]) -> Vec<u8>,
+    derive_secret: fn(secret: &[u8], label: &[u8], messages: ()) -> Vec<u8>,
+}
+impl CryptoProvider {
+    fn new<H: HkdfHasher>() -> Self {
+        CryptoProvider {
+            zeroed_of_hash_size: H::ZEROED,
+            hkdf_extract: H::extract,
+            derive_secret: derive_secret::<H>,
+        }
+    }
+}
+
+/**
+```text
+           0
+             |
+             v
+   PSK ->  HKDF-Extract = Early Secret
+             |
+             +-----> Derive-Secret(., "ext binder" | "res binder", "")
+             |                     = binder_key
+             |
+             +-----> Derive-Secret(., "c e traffic", ClientHello)
+             |                     = client_early_traffic_secret
+             |
+             +-----> Derive-Secret(., "e exp master", ClientHello)
+             |                     = early_exporter_master_secret
+             v
+       Derive-Secret(., "derived", "")
+             |
+             v
+   (EC)DHE -> HKDF-Extract = Handshake Secret
+             |
+             +-----> Derive-Secret(., "c hs traffic",
+             |                     ClientHello...ServerHello)
+             |                     = client_handshake_traffic_secret
+             |
+             +-----> Derive-Secret(., "s hs traffic",
+             |                     ClientHello...ServerHello)
+             |                     = server_handshake_traffic_secret
+             v
+       Derive-Secret(., "derived", "")
+             |
+             v
+   0 -> HKDF-Extract = Master Secret
+             |
+             +-----> Derive-Secret(., "c ap traffic",
+             |                     ClientHello...server Finished)
+             |                     = client_application_traffic_secret_0
+             |
+             +-----> Derive-Secret(., "s ap traffic",
+             |                     ClientHello...server Finished)
+             |                     = server_application_traffic_secret_0
+             |
+             +-----> Derive-Secret(., "exp master",
+             |                     ClientHello...server Finished)
+             |                     = exporter_master_secret
+             |
+             +-----> Derive-Secret(., "res master",
+                                   ClientHello...client Finished)
+                                   = resumption_master_secret
+```
+*/
+pub fn compute_keys(shared_secret: SharedSecret, algo: proto::CipherSuite) {
+    let provider = match algo {
+        proto::CipherSuite::TLS_AES_128_GCM_SHA256 => CryptoProvider::new::<sha2::Sha256>(),
+        proto::CipherSuite::TLS_AES_256_GCM_SHA384 => CryptoProvider::new::<sha2::Sha384>(),
+        proto::CipherSuite::TLS_CHACHA20_POLY1305_SHA256 => CryptoProvider::new::<sha2::Sha256>(),
+        proto::CipherSuite::TLS_AES_128_CCM_SHA256 => CryptoProvider::new::<sha2::Sha256>(),
+        proto::CipherSuite::TLS_AES_128_CCM_8_SHA256 => CryptoProvider::new::<sha2::Sha256>(),
     };
 
-    let derive_secret = |secret: &[u8], label: &[u8], messages: ()| {
-        hkdf_expand_label(secret, label, &[], 16) // todo: fix length
-    };
+    let early_secret =
+        (provider.hkdf_extract)(&provider.zeroed_of_hash_size, &provider.zeroed_of_hash_size);
+
+    let handhske_secret = (provider.hkdf_extract)(
+        &(provider.derive_secret)(&early_secret, b"derived", (/*empty*/)),
+        shared_secret.as_bytes(),
+    );
+
+    let client_handshake_traffic_secret = (provider.derive_secret)(
+        &handhske_secret,
+        b"c hs traffic",
+        (/*clienthello..serverhello*/),
+    );
+
+    let server_handshake_traffic_secret = (provider.derive_secret)(
+        &handhske_secret,
+        b"s hs traffic",
+        (/*clienthello..serverhello*/),
+    );
+
+    let master_secret = (provider.hkdf_extract)(
+        &(provider.derive_secret)(&handhske_secret, b"derived", (/*empty*/)),
+        &provider.zeroed_of_hash_size,
+    );
+
+    let client_application_traffic_secret_0 = (provider.derive_secret)(
+        &master_secret,
+        b"c ap traffic",
+        (/*clienthello..server finished*/),
+    );
+    let server_application_traffic_secret_0 = (provider.derive_secret)(
+        &master_secret,
+        b"s ap traffic",
+        (/*clienthello..server finished*/),
+    );
+
+
+    dbg!("keys");
 }
 
 pub struct AeadKey {
@@ -97,8 +253,6 @@ mod seq {
         }
     }
 }
-pub use seq::{SeqId, SeqIdGen};
-use x25519_dalek::SharedSecret;
 
 fn proto_algo_to_ring(algo: proto::CipherSuite) -> &'static aead::Algorithm {
     match algo {
diff --git a/src/lib.rs b/src/lib.rs
index 66f072d..9a06f9a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,5 @@
+#![allow(unused)]
+
 mod crypt;
 pub mod proto;
 
@@ -7,7 +9,6 @@ use std::{
     io::{self, Read, Write},
 };
 
-use crypt::{SeqId, SeqIdGen};
 use proto::CipherSuite;
 
 use crate::proto::TLSPlaintext;
@@ -61,7 +62,6 @@ mod stream_state {
 
         pub fn write_record(&mut self, plaintext: TLSPlaintext) -> Result<SeqId> {
             plaintext.write(&mut self.stream)?;
-            self.stream.flush()?;
             Ok(self.write_seq_id.next())
         }
 
@@ -305,7 +305,7 @@ impl<W: Read + Write> ClientSetupConnection<W> {
                         dh_shared_secret.as_bytes()
                     );
 
-                    crypt::compute_keys(dh_shared_secret);
+                    crypt::compute_keys(dh_shared_secret, cipher_suite);
 
                     ConnectState::WaitEncryptedExtensions
                 }
@@ -396,3 +396,10 @@ impl<R: Read> io::Read for LoggingWriter<R> {
         len
     }
 }
+
+pub trait LoggingWriterExt: Sized {
+    fn log(self) -> LoggingWriter<Self> {
+        LoggingWriter(self)
+    }
+}
+impl<W: io::Write> LoggingWriterExt for W {}
diff --git a/src/main.rs b/src/main.rs
index 2da4619..2ae6152 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,6 +2,9 @@ use std::net::TcpStream;
 
 // An example program that makes a shitty HTTP/1.1 request.
 fn main() {
-    let conn = tls::LoggingWriter(TcpStream::connect(("vps1.nilstrieb.dev", 443)).unwrap());
+    let conn = TcpStream::connect(("vps1.nilstrieb.dev", 443))
+        .unwrap()
+        //.log()
+        ;
     tls::ClientConnection::establish(conn, "vps1.nilstrieb.dev").unwrap();
 }
diff --git a/src/proto/ser_de.rs b/src/proto/ser_de.rs
index 2284c4a..5c97751 100644
--- a/src/proto/ser_de.rs
+++ b/src/proto/ser_de.rs
@@ -106,7 +106,7 @@ macro_rules! proto_enum {
         impl crate::proto::ser_de::Value for $name {
             fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
                 w.flush()?;
-                eprintln!("{}", stringify!($name));
+                //eprintln!("{}", stringify!($name));
                 mod discr_consts {
                     $(
                         #[allow(non_upper_case_globals)]
@@ -116,7 +116,7 @@ macro_rules! proto_enum {
 
                 let write_len = |_w: &mut W, _len: usize| -> io::Result<()> {
                     _w.flush()?;
-                    eprintln!("length");
+                    //eprintln!("length");
                     $(
                         <$len_ty>::try_from(_len).unwrap().write(_w)?;
                     )?
@@ -137,7 +137,7 @@ macro_rules! proto_enum {
 
                             $($(
                                 w.flush()?;
-                                eprintln!("{}", stringify!($field_name));
+                                //eprintln!("{}", stringify!($field_name));
                                 crate::proto::ser_de::Value::write($field_name, w)?;
                             )*)?