diff --git a/README.md b/README.md
index e087b0d..6248f25 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,11 @@
 SmartPGP is a free and open source implementation of the [OpenPGP card
 3.4 specification](https://gnupg.org/ftp/specs/OpenPGP-smart-card-application-3.4.pdf) in JavaCard.
 
+The main improvement introduced in OpenPGP card 3.x specification from
+previous version is the support of elliptic curve cryptography with
+several existing curves (NIST P-256, NIST P-384, NIST P-521, brainpool
+p256r1, brainpool p384r1 and brainpool p512r1).
+
 
 ## Features
 
@@ -26,6 +31,8 @@ of them depend on underlying hardware support and available
 
 - AES 128/256 bits deciphering primitive;
 
+- Secure messaging (see below).
+
 
 ## Default values
 
@@ -39,18 +46,47 @@ The SmartPGP applet is configured with the following default values:
 
 - RSA 2048 bits for PGP keys;
 
+- NIST P-256 for the secure messaging key.
+
 These values can be changed by modifying default values in the code
 (see the [Constants](src/fr/anssi/smartpgp/Constants.java)
 class).
 
 When the applet is installed, one can use the `smartpgp-cli` utility
 given in the `bin` directory to change these values. Keep in mind that
-when you change the algorithm attributes of a PGP key, the key and the 
-corresponding certificate are
+when you change the algorithm attributes of a PGP key or of the secure
+messaging key, the key and the corresponding certificate are
 erased. Also note that hard coded default values will be restored upon
 a factory reset.
 
 
+## Compliance with OpenPGP card 3.4 specification
+
+The SmartPGP applet implements the complete OpenPGP card 3.4
+specification, except the secure messaging related features:
+
+- Commands and responses protection is not implemented as described in
+  the specification. Motivation and implementation details are
+  explained in the
+  [secure messaging document](secure_messaging/smartpgp_sm.pdf);
+
+- A command protected by secure messaging is not granted admin
+  rights. Secure messaging can thus be used to protect communications
+  only, especially when the token is used contactless;
+
+- If and only if secure messaging static key and certificate have been
+  provisioned, all commands containing sensitive data (e.g. PIN code,
+  decrypted data, private key, ...) emitted through a contactless
+  interface must be protected by secure messaging or they will be
+  refused;
+
+- The `ACTIVATE FILE` with P1 = P2 = 0, as described in the
+  specification, resets everything except the secure messaging static
+  key and certificate. Complete reset, including these elements, can
+  be performed with `ACTIVATE FILE` with P1 = 0 and P2 = 1.
+
+
+
 # Application support
 
 Tokens following the OpenPGP card 3.4 specification are not yet fully
@@ -61,18 +97,28 @@ supported by most PGP applications.
 OpenPGP card 3.x is supported by [GnuPG](https://www.gnupg.org/)
 starting from version 2.1.16.
 
+The specific secure messaging of the SmartPGP applet is **not**
+supported at is not part of the OpenPGP card specification.
+
 ## OpenKeychain
 
 OpenPGP card 3.x is supported by [OpenKeychain](https://www.openkeychain.org/)
 starting from version 4.2.
 
+The secure messaging of the SmartPGP applet is fully supported in
+OpenKeychain. See the section below for more information on the setup process.
+
 
 # Content of the repository
 
 The repository contains several directories:
 
 - `bin` contains a Python library and command line tool called
-  `smartpgp-cli` to interact with an OpenPGP card 3.x;
+  `smartpgp-cli` to interact with an OpenPGP card 3.x but also to deal
+  with the specific secure messaging feature of the SmartPGP applet;
+  
+- `secure_messaging` contains documentation and example scripts to
+  play with the secure messaging feature of SmartPGP;
   
 - `src` contains the JavaCard source code of the SmartPGP applet;
 
@@ -131,7 +177,8 @@ resource consumption by tweaking the following variables:
 - `Constants.EXTENDED_CAPABILITIES`, bytes 5 and 6: the maximal size
   in bytes of a certificate associated to a key. Following the OpenPGP
   card specification, a certificate can be stored for each of the
-  three keys.
+  three keys. In SmartPGP, a fourth certificate is stored for secure
+  messaging.
 
 
 ## Building the CAP file
@@ -158,3 +205,93 @@ Be careful to use a valid AID according to the OpenPGP card
 specification (see section 4.2.1) for each card (`-create <AID>` with
 GlobalPlatformPro)
 
+
+
+# Setting up secure messaging with OpenKeychain
+
+## Secure messaging without token authentication
+
+Without token authentication, you are not protected against
+man-in-the-middle attack as your device cannot ensure it is
+communicating directly with a trusted token. Nevertheless, the
+communications with the token are still protected in confidentiality
+against passive attacks (i.e. trafic capture).
+
+If you want to test secure messaging without token authentication, you
+can use the following command to order the token to generate its
+secure messaging key on-board.
+
+`./smartpgp-cli -r X -I generate-sm-key -o pubkey.raw`
+
+In this case, you have to deactivate the certificate verification in
+OpenKeychain: go to "Parameters" > "Experimental features" and
+deactivate the option called "SmartPGP verify certificate".
+
+
+## Secure messaging with token authentication
+
+The `secure_messaging` directory contains a subdirectory called `pki`
+which contains two sample scripts to generate a certificate
+authority and token certificates.
+
+The sample scripts are given **only** for test purposes of the secure
+messaging feature with certificate verification. They require
+`openssl` to be installed on your system.
+
+If you want to use your own PKI, you have to generate a specific
+intermediate certificate authority to sign the certificates of your
+token(s). Then, you have to provision the complete certificate chain
+from this new intermediate CA to your root CA in OpenKeychain because
+the certificate verification implemented in the given patch does not
+rely on the system keystore.
+
+### Generate a sample CA key and certificate
+
+Change your current directory to the `pki` directory and execute the
+script `./generate_ca.sh`. It will produce a sample CA key in
+`PKI/private/ca.key.pem` and the corresponding certificate in
+`PKI/certs/ca.cert.pem`.
+
+### Generate a sample token key and certificate
+
+Change your current directory to the `pki` directory and execute the
+script
+
+`./generate_token.sh mycard1`
+
+where `mycard1` is some unique identifier for the token. It will
+produce a sample token key in `PKI/private/mycard1.key.pem` and the
+corresponding certificate in `PKI/certs/mycard1.cert.pem`.
+
+### Provision the token with its sample key and certificate
+
+Change your current directory to the `bin` directory and execute the
+following commands after replacing the reader number `X` by the number
+of the reader that contains your token, and the path to the `pki`
+directory used in previous sections.
+
+The following command imports the token key in the token.
+
+`./smartpgp-cli -r X -I -i path_to_the_pki_dir/PKI/private/mycard1.key.der put-sm-key`
+
+The following command imports the token certificate in the token.
+
+`./smartpgp-cli -r X -I -i path_to_the_pki_dir/PKI/certs/mycard1.cert.der put-sm-certificate`
+
+These commands have to be executed in this order because the key
+import clears any previously stored certificate.
+
+Once the token key is imported, you should remove the token private
+key from you system as there is no need to keep it outside of your
+token.
+
+### Install the CA in OpenKeychain
+
+- Upload the CA certificate `PKI/certs/ca.cert.pem` to your phone;
+
+- Go to "Parameters" > "Experimental features" and activate the option called "SmartPGP verify certificate`;
+
+- Click on "SmartPGP trusted authorities", and then on "+" at the top left;
+
+- Set a name for this authority and select the file you uploaded.
+
diff --git a/secure_messaging/pki/generate_ca.sh b/secure_messaging/pki/generate_ca.sh
new file mode 100755
index 0000000..3bd41c8
--- /dev/null
+++ b/secure_messaging/pki/generate_ca.sh
@@ -0,0 +1,29 @@
+#!/bin/bash
+
+CURVE=secp521r1
+DAYS=1825
+
+######
+
+DIR=PKI
+
+######
+
+set -e -u
+
+if [[ -e "$DIR/private/ca.key.pem" ]] ; then
+    echo "CA already exists, please remove it manually if you want to generate a new one" 1>&2
+    exit 2
+fi
+
+mkdir -p "$DIR/private" "$DIR/certs"
+
+openssl ecparam -name "$CURVE" -genkey -check -noout -outform pem -out "$DIR/private/ca.key.pem"
+
+openssl req -config openssl.cnf -extensions v3_ca -days $DAYS -new -x509 -sha256 -keyform pem -key "$DIR/private/ca.key.pem" -outform pem -out "$DIR/certs/ca.cert.pem"
+
+touch $DIR/index.txt
+
+echo 1000 > $DIR/serial
+
+echo 1000 > $DIR/crlnumber
diff --git a/secure_messaging/pki/generate_token.sh b/secure_messaging/pki/generate_token.sh
new file mode 100755
index 0000000..b434dad
--- /dev/null
+++ b/secure_messaging/pki/generate_token.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+
+CURVE=secp256r1
+DAYS=730
+
+######
+
+DIR=PKI
+
+######
+
+set -e  -u
+
+if [[ $# -lt 1 ]] ; then
+    echo "Missing card certificate identifier" 1>&2
+    exit 1
+fi
+if [[ $# -gt 1 ]] ; then
+    echo "Too many parameters" 1>&2
+    exit 2
+fi
+
+if [[ ! -e "$DIR/private/ca.key.pem" ]] ; then
+    echo "Missing CA (please execute generate_ca.sh)" 1>&2
+    exit 2
+fi
+
+
+NAME="$1"
+
+mkdir -p "$DIR/csr"
+
+openssl ecparam -name "$CURVE" -genkey -check -noout -outform der -out "$DIR/private/$NAME.key.der"
+
+openssl req -config openssl.cnf -new -sha256 -keyform der -key "$DIR/private/$NAME.key.der" -outform pem -out "$DIR/csr/$NAME.csr.pem"
+
+openssl ca -config openssl.cnf -extensions card_cert -days $DAYS -md sha256 -in "$DIR/csr/$NAME.csr.pem" -out "$DIR/certs/$NAME.cert.pem"
+
+openssl x509 -inform pem -in "$DIR/certs/$NAME.cert.pem" -outform der -out "$DIR/certs/$NAME.cert.der"
+
+rm "$DIR/certs/$NAME.cert.pem"
+
diff --git a/secure_messaging/pki/openssl.cnf b/secure_messaging/pki/openssl.cnf
new file mode 100644
index 0000000..bda6751
--- /dev/null
+++ b/secure_messaging/pki/openssl.cnf
@@ -0,0 +1,91 @@
+
+[ ca ]
+default_ca = CA_default
+
+[ CA_default ]
+# Directory and file locations.
+dir               = ./PKI/
+certs             = $dir/certs
+crl_dir           = $dir/crl
+new_certs_dir     = $dir/certs
+database          = $dir/index.txt
+serial            = $dir/serial
+RANDFILE          = $dir/private/.rand
+
+# The root key and root certificate.
+private_key       = $dir/private/ca.key.pem
+certificate       = $dir/certs/ca.cert.pem
+
+# For certificate revocation lists.
+crlnumber         = $dir/crlnumber
+crl               = $dir/crl/ca.crl.pem
+crl_extensions    = crl_ext
+default_crl_days  = 30
+
+# SHA-1 is deprecated, so use SHA-2 instead.
+default_md        = sha256
+
+name_opt          = ca_default
+cert_opt          = ca_default
+default_days      = 730
+preserve          = no
+policy            = policy_loose
+
+[ policy_loose ]
+countryName             = optional
+stateOrProvinceName     = optional
+localityName            = optional
+organizationName        = optional
+organizationalUnitName  = optional
+commonName              = supplied
+emailAddress            = optional
+
+[ req ]
+# Options for the `req` tool (`man req`).
+default_bits        = 2048
+distinguished_name  = req_distinguished_name
+string_mask         = utf8only
+
+# SHA-1 is deprecated, so use SHA-2 instead.
+default_md          = sha256
+
+# Extension to add when the -x509 option is used.
+x509_extensions     = v3_ca
+
+[ req_distinguished_name ]
+# See <https://en.wikipedia.org/wiki/Certificate_signing_request>.
+countryName                     = Country Name (2 letter code)
+stateOrProvinceName             = State or Province Name
+localityName                    = Locality Name
+0.organizationName              = Organization Name
+organizationalUnitName          = Organizational Unit Name
+commonName                      = Common Name
+emailAddress                    = Email Address
+
+# Optionally, specify some defaults.
+countryName_default             = 
+stateOrProvinceName_default     = 
+localityName_default            =
+0.organizationName_default      = 
+organizationalUnitName_default  =
+emailAddress_default            =
+
+[ v3_ca ]
+# Extensions for a typical CA (`man x509v3_config`).
+subjectKeyIdentifier = hash
+authorityKeyIdentifier = keyid:always,issuer
+basicConstraints = critical, CA:true, pathlen:1
+keyUsage = critical, digitalSignature, cRLSign, keyCertSign
+
+[ card_cert ]
+# Extensions for client certificates (`man x509v3_config`).
+basicConstraints = CA:FALSE
+nsCertType = client
+subjectKeyIdentifier = hash
+authorityKeyIdentifier = keyid,issuer
+keyUsage = critical, nonRepudiation
+
+[ crl_ext ]
+# Extension for CRLs (`man x509v3_config`).
+authorityKeyIdentifier=keyid:always
+