diff --git a/Cargo.lock b/Cargo.lock
index b512b73..7dd93ba 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -799,6 +799,7 @@ name = "rsh"
 version = "0.1.0"
 dependencies = [
  "ad-hoc-iter",
+ "base64 0.13.0",
  "bytes 1.0.1",
  "chacha20stream",
  "color-eyre",
diff --git a/Cargo.toml b/Cargo.toml
index d29c398..3271d69 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2018"
 
 [dependencies]
 ad-hoc-iter = "0.2.3"
+base64 = "0.13.0"
 bytes = { version = "1.0.1", features = ["serde"] }
 chacha20stream = { version = "2.1.0", features = ["async", "serde"] }
 color-eyre = "0.5.11"
diff --git a/src/ext/alloc.rs b/src/ext/alloc.rs
new file mode 100644
index 0000000..96613c2
--- /dev/null
+++ b/src/ext/alloc.rs
@@ -0,0 +1,91 @@
+//! Stack allocation helpers
+use super::*;
+
+/// Max size of memory allowed to be allocated on the stack.
+pub const STACK_MEM_ALLOC_MAX: usize = 2048; // 2KB
+
+/// A stack-allocated vector that spills onto the heap when needed.
+pub type StackVec<T> = SmallVec<[T; STACK_MEM_ALLOC_MAX]>;
+
+/// Allocate a local buffer initialised from `init`.
+pub fn alloc_local_with<T, U>(sz: usize, init: impl FnMut() -> T, within: impl FnOnce(&mut [T]) -> U) -> U
+{
+    if sz > STACK_MEM_ALLOC_MAX {
+	let mut memory: Vec<T> = iter::repeat_with(init).take(sz).collect();
+	within(&mut memory[..])
+    } else {
+	stackalloc::stackalloc_with(sz, init, within)
+    }
+}
+
+
+
+/// Allocate a local zero-initialised byte buffer
+pub fn alloc_local_bytes<U>(sz: usize, within: impl FnOnce(&mut [u8]) -> U) -> U
+{
+    if sz > STACK_MEM_ALLOC_MAX {
+	let mut memory: Vec<MaybeUninit<u8>> = vec_uninit(sz);
+	within(unsafe {
+	    std::ptr::write_bytes(memory.as_mut_ptr(), 0, sz);
+	    stackalloc::helpers::slice_assume_init_mut(&mut memory[..])
+	})
+    } else {
+	stackalloc::alloca_zeroed(sz, within)
+    }
+}
+
+
+/// Allocate a local zero-initialised buffer
+pub fn alloc_local_zeroed<T, U>(sz: usize, within: impl FnOnce(&mut [MaybeUninit<T>]) -> U) -> U
+{
+    let sz_bytes = mem::size_of::<T>() * sz;
+    if sz > STACK_MEM_ALLOC_MAX {
+	let mut memory = vec_uninit(sz);
+	unsafe {
+	    std::ptr::write_bytes(memory.as_mut_ptr(), 0, sz_bytes);
+	}
+	within(&mut memory[..])
+    } else {
+	stackalloc::alloca_zeroed(sz_bytes, move |buf| {
+	    unsafe {
+		debug_assert_eq!(buf.len() / mem::size_of::<T>(), sz);
+		within(std::slice::from_raw_parts_mut(buf.as_mut_ptr() as *mut MaybeUninit<T>, sz))
+	    }
+	})
+    }
+}
+
+
+/// Allocate a local uninitialised buffer
+pub fn alloc_local_uninit<T, U>(sz: usize, within: impl FnOnce(&mut [MaybeUninit<T>]) -> U) -> U
+{
+    if sz > STACK_MEM_ALLOC_MAX {
+	let mut memory = vec_uninit(sz);
+	within(&mut memory[..])
+    } else {
+	stackalloc::stackalloc_uninit(sz, within)
+    }
+}
+
+
+/// Allocate a local buffer initialised with `init`.
+pub fn alloc_local<T: Clone, U>(sz: usize, init: T, within: impl FnOnce(&mut [T]) -> U) -> U
+{
+    if sz > STACK_MEM_ALLOC_MAX {
+	let mut memory: Vec<T> = iter::repeat(init).take(sz).collect();
+	within(&mut memory[..])
+    } else {
+	stackalloc::stackalloc(sz, init, within)
+    }
+}
+
+/// Allocate a local buffer initialised with `T::default()`.
+pub fn alloc_local_with_default<T: Default, U>(sz: usize, within: impl FnOnce(&mut [T]) -> U) -> U
+{
+    if sz > STACK_MEM_ALLOC_MAX {
+	let mut memory: Vec<T> = iter::repeat_with(Default::default).take(sz).collect();
+	within(&mut memory[..])
+    } else {
+	stackalloc::stackalloc_with_default(sz, within)
+    }
+}
diff --git a/src/ext/hex.rs b/src/ext/hex.rs
new file mode 100644
index 0000000..1c1f277
--- /dev/null
+++ b/src/ext/hex.rs
@@ -0,0 +1,124 @@
+use std::{
+    mem,
+    iter::{
+	self, 
+	ExactSizeIterator,
+	FusedIterator,
+    },
+    slice,
+    fmt,
+};
+#[derive(Debug, Clone)]
+pub struct HexStringIter<I>(I, [u8; 2]);
+
+impl<I: Iterator<Item = u8>> HexStringIter<I>
+{
+    /// Write this hex string iterator to a formattable buffer
+    pub fn consume<F>(self, f: &mut F) -> fmt::Result
+    where F: std::fmt::Write
+    {
+	if self.1[0] != 0 {
+	    write!(f, "{}", self.1[0] as char)?;
+	}
+	if self.1[1] != 0 {
+	    write!(f, "{}", self.1[1] as char)?;
+	}
+
+	for x in self.0 {
+	    write!(f, "{:02x}", x)?;
+	}
+	
+	Ok(())
+    }
+
+    /// Consume into a string
+    pub fn into_string(self) -> String
+    {
+	let mut output = match self.size_hint() {
+	    (0, None) => String::new(),
+	    (_, Some(x)) |
+	    (x, None) => String::with_capacity(x),
+	};
+	self.consume(&mut output).unwrap();
+	output
+    }
+}
+
+pub trait HexStringIterExt<I>: Sized
+{
+    fn into_hex(self) -> HexStringIter<I>;
+}
+
+pub type HexStringSliceIter<'a> = HexStringIter<iter::Copied<slice::Iter<'a, u8>>>;
+
+pub trait HexStringSliceIterExt
+{
+    fn hex(&self) -> HexStringSliceIter<'_>;
+}
+
+impl<S> HexStringSliceIterExt for S
+where S: AsRef<[u8]>
+{
+    fn hex(&self) -> HexStringSliceIter<'_>
+    {
+	self.as_ref().iter().copied().into_hex()
+    }
+}
+
+impl<I: IntoIterator<Item=u8>> HexStringIterExt<I::IntoIter> for I
+{
+    #[inline] fn into_hex(self) -> HexStringIter<I::IntoIter> {
+	HexStringIter(self.into_iter(), [0u8; 2])
+    }
+}
+
+impl<I: Iterator<Item = u8>> Iterator for HexStringIter<I>
+{
+    type Item = char;
+    fn next(&mut self) -> Option<Self::Item>
+    {
+	match self.1 {
+	    [_, 0] => {
+		use std::io::Write;
+		write!(&mut self.1[..], "{:02x}", self.0.next()?).unwrap();
+
+		Some(mem::replace(&mut self.1[0], 0) as char)
+	    },
+	    [0, _] => Some(mem::replace(&mut self.1[1], 0) as char),
+	    _ => unreachable!(),
+	}
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+	let (l, h) = self.0.size_hint();
+
+	(l * 2, h.map(|x| x*2))
+    }
+}
+
+impl<I: Iterator<Item = u8> + ExactSizeIterator> ExactSizeIterator for HexStringIter<I>{}
+impl<I: Iterator<Item = u8> + FusedIterator> FusedIterator for HexStringIter<I>{}
+
+impl<I: Iterator<Item = u8>> From<HexStringIter<I>> for String
+{
+    fn from(from: HexStringIter<I>) -> Self
+    {
+	from.into_string()
+    }
+}
+
+impl<I: Iterator<Item = u8> + Clone> fmt::Display for HexStringIter<I>
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	self.clone().consume(f)
+    }
+}
+
+/*
+#[macro_export] macro_rules! prog1 {
+    ($first:expr, $($rest:expr);+ $(;)?) => {
+	($first, $( $rest ),+).0
+    }
+}
+*/
diff --git a/src/ext.rs b/src/ext/mod.rs
similarity index 53%
rename from src/ext.rs
rename to src/ext/mod.rs
index dc648b5..84bd83a 100644
--- a/src/ext.rs
+++ b/src/ext/mod.rs
@@ -4,11 +4,11 @@ use std::mem::{self, MaybeUninit};
 use std::iter;
 use smallvec::SmallVec;
 
-/// Max size of memory allowed to be allocated on the stack.
-pub const STACK_MEM_ALLOC_MAX: usize = 2048; // 2KB
+mod alloc;
+pub use alloc::*;
 
-/// A stack-allocated vector that spills onto the heap when needed.
-pub type StackVec<T> = SmallVec<[T; STACK_MEM_ALLOC_MAX]>;
+mod hex;
+pub use hex::*;
 
 /// A maybe-atom that can spill into a vector.
 pub type MaybeVec<T> = SmallVec<[T; 1]>;
@@ -23,89 +23,6 @@ pub fn vec_uninit<T>(sz: usize) -> Vec<MaybeUninit<T>>
     }
 }
 
-/// Allocate a local buffer initialised from `init`.
-pub fn alloc_local_with<T, U>(sz: usize, init: impl FnMut() -> T, within: impl FnOnce(&mut [T]) -> U) -> U
-{
-    if sz > STACK_MEM_ALLOC_MAX {
-	let mut memory: Vec<T> = iter::repeat_with(init).take(sz).collect();
-	within(&mut memory[..])
-    } else {
-	stackalloc::stackalloc_with(sz, init, within)
-    }
-}
-
-
-
-/// Allocate a local zero-initialised byte buffer
-pub fn alloc_local_bytes<U>(sz: usize, within: impl FnOnce(&mut [u8]) -> U) -> U
-{
-    if sz > STACK_MEM_ALLOC_MAX {
-	let mut memory: Vec<MaybeUninit<u8>> = vec_uninit(sz);
-	within(unsafe {
-	    std::ptr::write_bytes(memory.as_mut_ptr(), 0, sz);
-	    stackalloc::helpers::slice_assume_init_mut(&mut memory[..])
-	})
-    } else {
-	stackalloc::alloca_zeroed(sz, within)
-    }
-}
-
-
-/// Allocate a local zero-initialised buffer
-pub fn alloc_local_zeroed<T, U>(sz: usize, within: impl FnOnce(&mut [MaybeUninit<T>]) -> U) -> U
-{
-    let sz_bytes = mem::size_of::<T>() * sz;
-    if sz > STACK_MEM_ALLOC_MAX {
-	let mut memory = vec_uninit(sz);
-	unsafe {
-	    std::ptr::write_bytes(memory.as_mut_ptr(), 0, sz_bytes);
-	}
-	within(&mut memory[..])
-    } else {
-	stackalloc::alloca_zeroed(sz_bytes, move |buf| {
-	    unsafe {
-		debug_assert_eq!(buf.len() / mem::size_of::<T>(), sz);
-		within(std::slice::from_raw_parts_mut(buf.as_mut_ptr() as *mut MaybeUninit<T>, sz))
-	    }
-	})
-    }
-}
-
-
-/// Allocate a local uninitialised buffer
-pub fn alloc_local_uninit<T, U>(sz: usize, within: impl FnOnce(&mut [MaybeUninit<T>]) -> U) -> U
-{
-    if sz > STACK_MEM_ALLOC_MAX {
-	let mut memory = vec_uninit(sz);
-	within(&mut memory[..])
-    } else {
-	stackalloc::stackalloc_uninit(sz, within)
-    }
-}
-
-
-/// Allocate a local buffer initialised with `init`.
-pub fn alloc_local<T: Clone, U>(sz: usize, init: T, within: impl FnOnce(&mut [T]) -> U) -> U
-{
-    if sz > STACK_MEM_ALLOC_MAX {
-	let mut memory: Vec<T> = iter::repeat(init).take(sz).collect();
-	within(&mut memory[..])
-    } else {
-	stackalloc::stackalloc(sz, init, within)
-    }
-}
-
-/// Allocate a local buffer initialised with `T::default()`.
-pub fn alloc_local_with_default<T: Default, U>(sz: usize, within: impl FnOnce(&mut [T]) -> U) -> U
-{
-    if sz > STACK_MEM_ALLOC_MAX {
-	let mut memory: Vec<T> = iter::repeat_with(Default::default).take(sz).collect();
-	within(&mut memory[..])
-    } else {
-	stackalloc::stackalloc_with_default(sz, within)
-    }
-}
-
 /// Create a blanket-implementing trait that is a subtrait of any number of traits.
 ///
 /// # Usage
diff --git a/src/sock/enc.rs b/src/sock/enc.rs
index 892eb05..c068418 100644
--- a/src/sock/enc.rs
+++ b/src/sock/enc.rs
@@ -2,8 +2,14 @@
 use super::*;
 use cryptohelpers::{
     rsa::{
+	self,
 	RsaPublicKey,
 	RsaPrivateKey,
+	
+	openssl::{
+	    symm::Crypter,
+	    error::ErrorStack,
+	},
     },
     sha256,
 };
@@ -12,6 +18,8 @@ use chacha20stream::{
     AsyncSource,
 
     Key, IV,
+
+    cha,
 };
 use std::sync::Arc;
 use tokio::{
@@ -20,25 +28,24 @@ use tokio::{
 	RwLockReadGuard,
 	RwLockWriteGuard,
     },
-    io::{
-	DuplexStream,
-    },
 };
 use std::{
     io,
+    fmt,
     task::{
 	Context, Poll,
     },
     pin::Pin,
-    marker::{
-	Unpin,
-	PhantomPinned,
-    },
+    marker::Unpin,
 };
+use smallvec::SmallVec;
 
 /// Size of a single RSA ciphertext.
 pub const RSA_CIPHERTEXT_SIZE: usize = 512;
 
+/// A single, full block of RSA ciphertext.
+type RsaCiphertextBlock = [u8; RSA_CIPHERTEXT_SIZE];
+
 /// Max size to read when exchanging keys
 const TRANS_KEY_MAX_SIZE: usize = 4096;
 
@@ -55,7 +62,7 @@ struct ESockState {
     encw: bool,
 }
 
-/// Contains a Key and IV that can be serialized and then encrypted
+/// Contains a cc20 Key and IV that can be serialized and then encrypted
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 struct ESockSessionKey
 {
@@ -63,6 +70,67 @@ struct ESockSessionKey
     iv: IV,
 }
 
+impl fmt::Display for ESockSessionKey
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	write!(f, "Key: {}, IV: {}", self.key.hex(), self.iv.hex())
+    }
+}
+
+
+impl ESockSessionKey
+{
+    /// Generate a new cc20 key + iv,
+    pub fn generate() -> Self
+    {
+	let (key,iv) = cha::keygen();
+	Self{key,iv}
+    }
+
+    /// Generate an encryption device
+    pub fn to_decrypter(&self) -> Result<Crypter, ErrorStack>
+    {
+	cha::decrypter(&self.key, &self.iv)
+    }
+    
+    /// Generate an encryption device
+    pub fn to_encrypter(&self) -> Result<Crypter, ErrorStack>
+    {
+	cha::encrypter(&self.key, &self.iv)
+    }
+
+    /// Encrypt with RSA
+    pub fn to_ciphertext<K: ?Sized + rsa::PublicKey>(&self, rsa_key: &K) -> eyre::Result<RsaCiphertextBlock>
+    {
+	let mut output = [0u8; RSA_CIPHERTEXT_SIZE];
+	let mut temp = SmallVec::<[u8; RSA_CIPHERTEXT_SIZE]>::new(); // We know size will fit into here.
+	serde_cbor::to_writer(&mut temp, self)
+	    .wrap_err(eyre!("Failed to CBOR encode session key to buffer"))
+	    .with_section(|| self.clone().header("Session key was"))?;
+	debug_assert!(temp.len() < RSA_CIPHERTEXT_SIZE);
+
+	let _wr = rsa::encrypt_slice_sync(&temp, rsa_key, &mut &mut output[..])
+	    .wrap_err(eyre!("Failed to encrypt session key with RSA public key"))
+	    .with_section(|| self.clone().header("Session key was"))
+	    .with_section({let temp = temp.len(); move || temp.header("Encoded data size was")})
+	    .with_section(move || base64::encode(temp).header("Encoded data (base64) was"))
+	    ?;
+	debug_assert_eq!(_wr, output.len());
+
+	Ok(output)
+    }
+
+    /// Decrypt from RSA
+    pub fn from_ciphertext<K: ?Sized + rsa::PrivateKey>(data: &[u8; RSA_CIPHERTEXT_SIZE], rsa_key: &K) -> eyre::Result<Self>
+    where <K as rsa::PublicKey>::KeyType: rsa::openssl::pkey::HasPrivate //ugh, why do we have to have this bound??? it should be implied ffs... :/
+    {
+	let mut temp = SmallVec::<[u8; RSA_CIPHERTEXT_SIZE]>::new();
+	rsa::decrypt_slice_sync(data, rsa_key, &mut temp)?;
+	Ok(serde_cbor::from_slice(&temp[..])?)
+    }
+}
+
 /// A tx+rx socket.
 #[pin_project]
 #[derive(Debug)]
@@ -88,32 +156,7 @@ impl<W: AsyncWrite, R: AsyncRead> ESock<W, R>
     {
 	(self.tx.inner_mut(), self.rx.inner_mut())
     }
-
-    /// Create a future that exchanges keys
-    pub fn exchange_unsafe(&mut self) -> Exchange<'_, W, R>
-    {
-	let us = self.info.us.get_public_parts();
-	todo!("Currently unimplemented")
-	/*
-	    Exchange{
-	    sock: self,
-	    write_buf: Default::default(),
-	    read_buf: Default::default(),
-	    _pin: PhantomPinned,
-
-	    read_state: Default::default(),
-	    write_state: Default::default(),
-
-	    us,
-	    them: None,
-	    us_written: Default::default(),
-	    us_buf: (),
-	    write_sz_num: (),
-	    write_sz_buf: (),
-	    read_sz_buf: (),
-    }*/
-    }
-
+    
     ///Get a mutable ref to unencrypted read+write
     fn unencrypted(&mut self) -> (&mut W, &mut R)
     {
@@ -143,8 +186,16 @@ impl<W: AsyncWrite+ Unpin, R: AsyncRead + Unpin> ESock<W, R>
     /// Enable write encryption
     pub async fn set_encrypted_write(&mut self, set: bool) -> eyre::Result<()>
     {
+	use tokio::prelude::*;
 	if set {
-	    let (key, iv) = ((),());
+	    let session_key = ESockSessionKey::generate();
+	    let data = session_key.to_ciphertext(self.info.them.as_ref().expect("Cannot set encrypted write when keys have not been exchanged"))?;
+	    let crypter = session_key.to_encrypter()?;
+	    // Send rsa `data` over unencrypted endpoint
+	    self.unencrypted().0.write_all(&data[..]).await?;
+	    // Set crypter of `tx` to `session_key`.
+	    *self.tx.crypter_mut() = crypter;
+	    // Set `encw` to true
 	    self.state.encw = true;
 	    Ok(())
 	} else {
@@ -152,6 +203,30 @@ impl<W: AsyncWrite+ Unpin, R: AsyncRead + Unpin> ESock<W, R>
 	    Ok(())
 	}
     }
+
+    /// Enable read encryption
+    ///
+    /// The other endpoint must have sent a `set_encrypted_write()`
+    pub async fn set_encrypted_read(&mut self, set: bool) -> eyre::Result<()>
+    {
+	use tokio::prelude::*;
+	if set {
+	    let mut data = [0u8; RSA_CIPHERTEXT_SIZE];
+	    // Read `data` from unencrypted endpoint
+	    self.unencrypted().1.read_exact(&mut data[..]).await?;
+	    // Decrypt `data`
+	    let session_key = ESockSessionKey::from_ciphertext(&data, &self.info.us)?;
+	    // Set crypter of `rx` to `session_key`.
+	    *self.rx.crypter_mut() = session_key.to_decrypter()?;
+	    // Set `encr` to true
+	    self.state.encr = true;
+	    Ok(())
+	} else {
+
+	    self.state.encr = false;
+	    Ok(())
+	}
+    }
     
     /// Get dynamic ref to unencrypted write+read
     fn unencrypted_dyn(&mut self) -> (&mut (dyn AsyncWrite + Unpin + '_), &mut (dyn AsyncRead + Unpin + '_))
@@ -208,117 +283,6 @@ impl<W: AsyncWrite+ Unpin, R: AsyncRead + Unpin> ESock<W, R>
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash, Copy, PartialOrd, Ord)]
-enum ExchangeState
-{
-    /// We are currently reading/writing the buffer's size
-    BufferSize,
-    /// We are currently reading/writing the buffer itself
-    Buffer,
-}
-
-impl Default for ExchangeState
-{
-    #[inline]
-    fn default() -> Self
-    {
-	Self::BufferSize
-    }
-}
-
-
-#[pin_project]
-#[derive(Debug)]
-pub struct Exchange<'a, W, R>
-{
-    sock: &'a mut ESock<W, R>,
-
-    us: RsaPublicKey,
-
-    us_written: usize,
-    us_buf: Vec<u8>,
-    
-    /// The return value
-    them: Option<RsaPublicKey>,
-
-    write_sz_num: usize,
-    write_sz_buf: [u8; std::mem::size_of::<u64>()],
-    read_sz_buf: [u8; std::mem::size_of::<u64>()],
-
-    read_buf: Vec<u8>,
-    
-    write_state: ExchangeState,
-    read_state: ExchangeState,
-
-    #[pin] _pin: PhantomPinned,
-}
-
-/*
-impl<'a, W: AsyncWrite, R: AsyncRead> Future for Exchange<'a, W, R>
-{
-type Output = eyre::Result<()>;
-fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-use futures::ready;
-let this = self.project();
-let (tx, rx) = {
-let sock = this.sock;
-//XXX: Idk if this is safe?
-unsafe {
-(Pin::new_unchecked(&mut sock.tx), Pin::new_unchecked(&mut sock.rx))
-	    }
-	};
-
-	if this.us_buf.is_empty() {
-	    *this.us_buf = this.us.to_bytes();
-	}
-	
-	let poll_write = loop {
-	    break match this.write_state {
-		ExchangeState::BufferSize => {
-		    if *this.write_sz_num == 0 {
-			*this.write_sz_buf = u64::try_from(this.us_buf.len())?.to_be_bytes();
-		    }
-		    // Write this to tx.
-		    match tx.poll_write(cx, &this.write_sz_buf[(*this.write_sz_num)..]) {
-			x @ Poll::Ready(Ok(n)) => {
-			    *this.write_sz_num+=n;
-			    if *this.write_sz_num == this.write_sz_buf.len() {
-				// We've written all the size bytes, continue to writing the buffer bytes.
-				*this.write_state = ExchangeState::Buffer;
-				continue;
-			    }
-
-			    x
-			},
-			x => x,
-		    }
-		},
-		ExchangeState::Buffer => {
-		    match tx.poll_write(cx, &this.us_buf[(*this.us_written)..]) {
-			x @ Poll::Ready(Ok(n)) => {
-			    if *this.us_written == this.us.len() {
-				
-			    }
-
-			    x
-			},
-			x=> x,
-		    }
-		},
-	    }
-	};
-	let poll_read = match this.read_state {
-	    ExchangeState::BufferSize => {
-		
-	    },
-	    ExchangeState::Buffer => {
-		
-	    },
-	};
-	todo!("This is going to be dificult to implement... We don't have access to write_all and read_exact")
-    }
-}
-*/
 /// Write half for `ESock`.
 #[pin_project]
 #[derive(Debug)]