diff --git a/Cargo.toml b/Cargo.toml
index a0d95aa..59a8a89 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,6 +14,7 @@ minidom = "0.4.1"
 jid = "0.2.0"
 base64 = "0.5.0"
 digest = "0.5.0"
+sha-1 = "0.3.0"
 sha2 = "0.5.0"
 sha3 = "0.5.0"
 blake2 = "0.5.0"
diff --git a/src/caps.rs b/src/caps.rs
new file mode 100644
index 0000000..d17cb50
--- /dev/null
+++ b/src/caps.rs
@@ -0,0 +1,296 @@
+// Copyright (c) 2017 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+use std::convert::TryFrom;
+
+use disco::{Feature, Identity, Disco};
+use data_forms::DataForm;
+use hashes::{Hash, Algo};
+
+use minidom::Element;
+use error::Error;
+use ns;
+use base64;
+
+use sha_1::Sha1;
+use sha2::{Sha256, Sha512};
+use sha3::{Sha3_256, Sha3_512};
+use blake2::Blake2b;
+use digest::{Digest, VariableOutput};
+
+#[derive(Debug, Clone)]
+pub struct Caps {
+    pub ext: Option<String>,
+    pub node: String,
+    pub hash: Hash,
+}
+
+impl TryFrom<Element> for Caps {
+    type Error = Error;
+
+    fn try_from(elem: Element) -> Result<Caps, Error> {
+        if !elem.is("c", ns::CAPS) {
+            return Err(Error::ParseError("This is not a caps element."));
+        }
+        for _ in elem.children() {
+            return Err(Error::ParseError("Unknown child in caps element."));
+        }
+        let hash = get_attr!(elem, "hash", required);
+        let ver: String = get_attr!(elem, "ver", required);
+        let hash = Hash {
+            algo: hash,
+            hash: base64::decode(&ver)?,
+        };
+        Ok(Caps {
+            ext: get_attr!(elem, "ext", optional),
+            node: get_attr!(elem, "node", required),
+            hash: hash,
+        })
+    }
+}
+
+impl From<Caps> for Element {
+    fn from(caps: Caps) -> Element {
+        Element::builder("c")
+                .ns(ns::CAPS)
+                .attr("ext", caps.ext)
+                .attr("hash", caps.hash.algo)
+                .attr("node", caps.node)
+                .attr("ver", base64::encode(&caps.hash.hash))
+                .build()
+    }
+}
+
+fn compute_item(field: &str) -> Vec<u8> {
+    let mut bytes = field.as_bytes().to_vec();
+    bytes.push(b'<');
+    bytes
+}
+
+fn compute_items<T, F: Fn(&T) -> Vec<u8>>(things: &[T], encode: F) -> Vec<u8> {
+    let mut string: Vec<u8> = vec!();
+    let mut accumulator: Vec<Vec<u8>> = vec!();
+    for thing in things {
+        let bytes = encode(thing);
+        accumulator.push(bytes);
+    }
+    // This works using the expected i;octet collation.
+    accumulator.sort();
+    for mut bytes in accumulator {
+        string.append(&mut bytes);
+    }
+    string
+}
+
+fn compute_features(features: &[Feature]) -> Vec<u8> {
+    compute_items(features, |feature| compute_item(&feature.var))
+}
+
+fn compute_identities(identities: &[Identity]) -> Vec<u8> {
+    compute_items(identities, |identity| {
+        let string = format!("{}/{}/{}/{}", identity.category, identity.type_, identity.xml_lang, match identity.name { Some(ref name) => name.clone(), None => String::new() });
+        let bytes = string.as_bytes();
+        let mut vec = Vec::with_capacity(bytes.len());
+        vec.extend_from_slice(bytes);
+        vec.push(b'<');
+        vec
+    })
+}
+
+fn compute_extensions(extensions: &[DataForm]) -> Vec<u8> {
+    compute_items(extensions, |extension| {
+        let mut bytes = vec!();
+        // TODO: maybe handle the error case?
+        if let Some(ref form_type) = extension.form_type {
+            bytes.extend_from_slice(form_type.as_bytes());
+        }
+        bytes.push(b'<');
+        for field in extension.fields.clone() {
+            if field.var == "FORM_TYPE" {
+                continue;
+            }
+            bytes.append(&mut compute_item(&field.var));
+            bytes.append(&mut compute_items(&field.values,
+                                            |value| compute_item(value)));
+        }
+        bytes
+    })
+}
+
+pub fn compute_disco(disco: &Disco) -> Vec<u8> {
+    let identities_string = compute_identities(&disco.identities);
+    let features_string = compute_features(&disco.features);
+    let extensions_string = compute_extensions(&disco.extensions);
+
+    let mut final_string = vec!();
+    final_string.extend(identities_string);
+    final_string.extend(features_string);
+    final_string.extend(extensions_string);
+    final_string
+}
+
+fn get_hash_vec(hash: &[u8]) -> Vec<u8> {
+    let mut vec = Vec::with_capacity(hash.len());
+    vec.extend_from_slice(hash);
+    vec
+}
+
+pub fn hash_caps(data: &[u8], algo: Algo) -> Result<Hash, String> {
+    Ok(Hash {
+        hash: match algo {
+            Algo::Sha_1 => {
+                let mut hasher = Sha1::default();
+                hasher.input(data);
+                let hash = hasher.result();
+                get_hash_vec(hash.as_slice())
+            },
+            Algo::Sha_256 => {
+                let mut hasher = Sha256::default();
+                hasher.input(data);
+                let hash = hasher.result();
+                get_hash_vec(hash.as_slice())
+            },
+            Algo::Sha_512 => {
+                let mut hasher = Sha512::default();
+                hasher.input(data);
+                let hash = hasher.result();
+                get_hash_vec(hash.as_slice())
+            },
+            Algo::Sha3_256 => {
+                let mut hasher = Sha3_256::default();
+                hasher.input(data);
+                let hash = hasher.result();
+                get_hash_vec(hash.as_slice())
+            },
+            Algo::Sha3_512 => {
+                let mut hasher = Sha3_512::default();
+                hasher.input(data);
+                let hash = hasher.result();
+                get_hash_vec(hash.as_slice())
+            },
+            Algo::Blake2b_256 => {
+                let mut hasher = Blake2b::default();
+                hasher.input(data);
+                let mut buf: [u8; 32] = [0; 32];
+                let hash = hasher.variable_result(&mut buf).unwrap();
+                get_hash_vec(hash)
+            },
+            Algo::Blake2b_512 => {
+                let mut hasher = Blake2b::default();
+                hasher.input(data);
+                let mut buf: [u8; 64] = [0; 64];
+                let hash = hasher.variable_result(&mut buf).unwrap();
+                get_hash_vec(hash)
+            },
+            Algo::Unknown(algo) => return Err(format!("Unknown algorithm: {}.", algo)),
+        },
+        algo: algo,
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use caps;
+    use base64;
+
+    #[test]
+    fn test_parse() {
+        let elem: Element = "<c xmlns='http://jabber.org/protocol/caps' hash='sha-256' node='coucou' ver='K1Njy3HZBThlo4moOD5gBGhn0U0oK7/CbfLlIUDi6o4='/>".parse().unwrap();
+        let caps = Caps::try_from(elem).unwrap();
+        assert_eq!(caps.node, String::from("coucou"));
+        assert_eq!(caps.hash.algo, Algo::Sha_256);
+        assert_eq!(caps.hash.hash, base64::decode("K1Njy3HZBThlo4moOD5gBGhn0U0oK7/CbfLlIUDi6o4=").unwrap());
+    }
+
+    #[test]
+    fn test_invalid_child() {
+        let elem: Element = "<c xmlns='http://jabber.org/protocol/caps'><hash xmlns='urn:xmpp:hashes:2' algo='sha-256'>K1Njy3HZBThlo4moOD5gBGhn0U0oK7/CbfLlIUDi6o4=</hash></c>".parse().unwrap();
+        let error = Caps::try_from(elem).unwrap_err();
+        let message = match error {
+            Error::ParseError(string) => string,
+            _ => panic!(),
+        };
+        assert_eq!(message, "Unknown child in caps element.");
+    }
+
+    #[test]
+    fn test_simple() {
+        let elem: Element = "<query xmlns='http://jabber.org/protocol/disco#info'><identity category='client' type='pc'/><feature var='http://jabber.org/protocol/disco#info'/></query>".parse().unwrap();
+        let disco = Disco::try_from(elem).unwrap();
+        let caps = caps::compute_disco(&disco);
+        assert_eq!(caps.len(), 50);
+    }
+
+    #[test]
+    fn test_xep_5_2() {
+        let elem: Element = r#"
+<query xmlns='http://jabber.org/protocol/disco#info'
+       node='http://psi-im.org#q07IKJEyjvHSyhy//CH0CxmKi8w='>
+  <identity category='client' name='Exodus 0.9.1' type='pc'/>
+  <feature var='http://jabber.org/protocol/caps'/>
+  <feature var='http://jabber.org/protocol/disco#info'/>
+  <feature var='http://jabber.org/protocol/disco#items'/>
+  <feature var='http://jabber.org/protocol/muc'/>
+</query>
+"#.parse().unwrap();
+        
+        let data = b"client/pc//Exodus 0.9.1<http://jabber.org/protocol/caps<http://jabber.org/protocol/disco#info<http://jabber.org/protocol/disco#items<http://jabber.org/protocol/muc<";
+        let mut expected = Vec::with_capacity(data.len());
+        expected.extend_from_slice(data);
+        let disco = Disco::try_from(elem).unwrap();
+        let caps = caps::compute_disco(&disco);
+        assert_eq!(caps, expected);
+
+        let sha_1 = caps::hash_caps(&caps, Algo::Sha_1).unwrap();
+        assert_eq!(sha_1.hash, base64::decode("QgayPKawpkPSDYmwT/WM94uAlu0=").unwrap());
+    }
+
+    #[test]
+    fn test_xep_5_3() {
+        let elem: Element = r#"
+<query xmlns='http://jabber.org/protocol/disco#info'
+       node='http://psi-im.org#q07IKJEyjvHSyhy//CH0CxmKi8w='>
+  <identity xml:lang='en' category='client' name='Psi 0.11' type='pc'/>
+  <identity xml:lang='el' category='client' name='Ψ 0.11' type='pc'/>
+  <feature var='http://jabber.org/protocol/caps'/>
+  <feature var='http://jabber.org/protocol/disco#info'/>
+  <feature var='http://jabber.org/protocol/disco#items'/>
+  <feature var='http://jabber.org/protocol/muc'/>
+  <x xmlns='jabber:x:data' type='result'>
+    <field var='FORM_TYPE' type='hidden'>
+      <value>urn:xmpp:dataforms:softwareinfo</value>
+    </field>
+    <field var='ip_version'>
+      <value>ipv4</value>
+      <value>ipv6</value>
+    </field>
+    <field var='os'>
+      <value>Mac</value>
+    </field>
+    <field var='os_version'>
+      <value>10.5.1</value>
+    </field>
+    <field var='software'>
+      <value>Psi</value>
+    </field>
+    <field var='software_version'>
+      <value>0.11</value>
+    </field>
+  </x>
+</query>
+"#.parse().unwrap();
+        let data = b"client/pc/el/\xce\xa8 0.11<client/pc/en/Psi 0.11<http://jabber.org/protocol/caps<http://jabber.org/protocol/disco#info<http://jabber.org/protocol/disco#items<http://jabber.org/protocol/muc<urn:xmpp:dataforms:softwareinfo<ip_version<ipv4<ipv6<os<Mac<os_version<10.5.1<software<Psi<software_version<0.11<";
+        let mut expected = Vec::with_capacity(data.len());
+        expected.extend_from_slice(data);
+        let disco = Disco::try_from(elem).unwrap();
+        let caps = caps::compute_disco(&disco);
+        assert_eq!(caps, expected);
+
+        let sha_1 = caps::hash_caps(&caps, Algo::Sha_1).unwrap();
+        assert_eq!(sha_1.hash, base64::decode("q07IKJEyjvHSyhy//CH0CxmKi8w=").unwrap());
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 2eb2aec..363dfec 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,6 +18,7 @@ extern crate minidom;
 extern crate jid;
 extern crate base64;
 extern crate digest;
+extern crate sha_1;
 extern crate sha2;
 extern crate sha3;
 extern crate blake2;
@@ -75,6 +76,9 @@ pub mod rsm;
 /// XEP-0085: Chat State Notifications
 pub mod chatstates;
 
+/// XEP-0115: Entity Capabilities
+pub mod caps;
+
 /// XEP-0166: Jingle
 pub mod jingle;
 
diff --git a/src/ns.rs b/src/ns.rs
index b51c653..99865ae 100644
--- a/src/ns.rs
+++ b/src/ns.rs
@@ -24,6 +24,9 @@ pub const RSM: &'static str = "http://jabber.org/protocol/rsm";
 /// XEP-0085: Chat State Notifications
 pub const CHATSTATES: &'static str = "http://jabber.org/protocol/chatstates";
 
+/// XEP-0115: Entity Capabilities
+pub const CAPS: &'static str = "http://jabber.org/protocol/caps";
+
 /// XEP-0166: Jingle
 pub const JINGLE: &'static str = "urn:xmpp:jingle:1";