diff --git a/README.rst b/README.rst
index 58c52cd..59c6641 100644
--- a/README.rst
+++ b/README.rst
@@ -1,9 +1,7 @@
 httpie-oauth
-===========
+============
 
-OAuth plugin for `HTTPie <https://httpie.org/>`_.
-
-It currently provides support for OAuth 1.0a 2-legged.
+OAuth 1.0a two-legged plugin for `HTTPie <https://httpie.org/>`_.
 
 
 Installation
@@ -14,16 +12,83 @@ Installation
     $ pip install httpie-oauth
 
 
-You should now see ``oauth1`` under ``--auth-type`` in ``$ http --help`` output.
+You should now see ``oauth1`` under ``--auth-type`` in the
+``$ http --help`` output.
+
+To be able to use the RSA-SHA1 signature type, also install **PyJWT**
+and PyCA's **cryptography** package.
+
+.. code-block:: bash
+
+    $ pip install pyjwt
+    $ pip install cryptography
 
+On CentOS 7, it might be easier to use *yum* to install "epel-release"
+and then the "python2-cryptography" packages, since to *pip install* it
+requires C code to be compiled.
 
 Usage
 -----
 
+HMAC-SHA1
+.........
+
+To use the HMAC-SHA1 signature method, in the ``--auth`` parameter
+provide the client-key, a single colon and the client-secret.
+
 .. code-block:: bash
 
     $ http --auth-type=oauth1 --auth='client-key:client-secret' example.org
 
+It will interactively prompt for the client-secret, if there is no colon.
+If the password starts with a colon, use this interactive method to enter it
+(otherwise the extra colon will cause it to use RSA-SHA1 instead of HMAC-SHA1).
+
+RSA-SHA1
+........
+
+To use the RSA-SHA1 signature method, in the ``--auth`` parameter
+provide the client key, two colons and the name of a file containing
+the RSA private key. The file must contain a PEM formatted RSA private
+key.
+
+.. code-block:: bash
+
+    $ http --auth-type=oauth1 --auth='client-key::filename' example.org
+
+It will interactively prompt for the filename, if there is no value
+after the two colons.
+
+The filename can also be a relative or absolute path to the file.
+
+Passphrase protected private keys are not supported.
+
+Including the client key in the private key file
+++++++++++++++++++++++++++++++++++++++++++++++++
+
+If the client key in the ``--auth`` parameter is empty (i.e. the
+option argument is just two colons and the filename), the
+``oauth_consumer_key`` parameter from the file is used.  It must
+appear in the file before the private key.
+
+For example, if the private key file contains something like this:
+
+::
+
+    oauth_consumer_key: myconsumerkey
+    -----BEGIN RSA PRIVATE KEY-----
+    ...
+    -----END RSA PRIVATE KEY-----
+
+It can be used with this command:
+
+.. code-block:: bash
+
+    $ http --auth-type=oauth1 --auth=::filename example.org
+
+
+HTTPie Sessions
+...............
 
 You can also use `HTTPie sessions <https://httpie.org/doc#sessions>`_:
 
@@ -35,3 +100,16 @@ You can also use `HTTPie sessions <https://httpie.org/doc#sessions>`_:
     # Re-use auth
     $ http --session=logged-in POST example.org hello=world
 
+
+Troubleshooting
+...............
+
+ImportError: No module named jwt.algorithms
++++++++++++++++++++++++++++++++++++++++++++
+
+The *PyJWT* module is not available. Please install it.
+
+AttributeError: 'module' object has no attribute 'RSAAlgorithm'
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+The PyCA's *cryptography* module is not available. Please install it.
diff --git a/httpie_oauth.py b/httpie_oauth.py
index 47cdc45..acec84d 100644
--- a/httpie_oauth.py
+++ b/httpie_oauth.py
@@ -1,12 +1,26 @@
 """
-OAuth plugin for HTTPie.
+OAuth 1.0a 2-legged plugin for HTTPie.
+
+Supports HMAC-SHA1 and RSA-SHA1 signature methods.
+
+If the authentication parameter is "username:password" then HMAC-SHA1 is used.
+If the password is omitted (i.e. --auth username is provided), the user is
+prompted for the password.
+
+If the authentication parameter is "username::filename" (double colon between
+the username and the filename) then RSA-SHA1 is used, and the PEM formatted
+private key is read from that file. If the filename is omitted
+(i.e. --auth username:: is provided), the user is prompted for
+the filename. The username is used as the oauth_client_key OAuth parameter.
 
 """
+import string
+import sys
 from httpie.plugins import AuthPlugin
 from requests_oauthlib import OAuth1
+from oauthlib.oauth1 import SIGNATURE_RSA
 
-
-__version__ = '1.0.2'
+__version__ = '2.0.0'
 __author__ = 'Jakub Roztocil'
 __licence__ = 'BSD'
 
@@ -15,7 +29,147 @@ class OAuth1Plugin(AuthPlugin):
 
     name = 'OAuth 1.0a 2-legged'
     auth_type = 'oauth1'
-    description = ''
+    description =\
+        '--auth user:HMAC-SHA1_secret or --auth user::RSA-SHA1_privateKeyFile'
+
+    def get_auth(self, username=None, password=None):
+        """
+        Generate OAuth 1.0a 2-legged authentication for HTTPie.
+
+        Note: Passpharse protected private keys are not yet supported.
+        Before support can be implemented, the PyJWT, oauthlib and
+        requests_oauthlib modules need to be updated.
+        The passphrase needs to be obtained here and passed
+        through to PyJWT's jwt/algorithms.py, line 168, where currently it
+        passes into load_pem_private_key a hardcoded value of None for the
+        password.
+        To get it to there, many places in oauthlib's oauth1/rfc5849/__init__.py
+        and oauth1/rfc5849/signature.py, as well as in requests_oauthlib's
+        oauth1_auth.py, need to be updated to pass it through.
+
+        :param username: username
+        :param password: password, or colon followed by a filename
+        :return: requests_oauthlib.oauth1_auth.OAuth1 object
+        """
+        if not password.startswith(':'):
+            # HMAC-SHA1 signature method (--auth client-key:client-secret)
+            return OAuth1(client_key=username, client_secret=password)
+
+        else:
+            # RSA-SHA1 signature method (--auth oauth_consumer_key::filename)
+            filename = password[1:]
+            if len(filename) == 0:
+                # Prompt for filename of RSA private key
+                try:
+                    filename = raw_input('http: filename of RSA private key: ')
+                except EOFError:  # if ^D entered
+                    sys.exit(1)
+
+            username, key = OAuth1Plugin.read_private_key(username, filename)
+
+            return OAuth1(client_key=username,
+                          signature_method=SIGNATURE_RSA,
+                          rsa_key=key)
+
+    @staticmethod
+    def read_private_key(username, filename):
+        """
+        Check if the key is a recognised private key format.
+
+        Prints an error message to stderr and exits if it is not. Uses
+        crude checks to try and generate more useful error messages.
+
+        :param username: username to use
+        :param filename: file to read private key from
+        :return: PEM formatted private key
+        """
+        PEM_PRIVATE_KEY_BEGINNING = '-----BEGIN RSA PRIVATE KEY-----'
+        PEM_PRIVATE_KEY_ENDING = '-----END RSA PRIVATE KEY-----'
+        ATTR_NAME = 'oauth_consumer_key'
+
+        try:
+            data = open(filename).read()
+
+            key_start = data.find(PEM_PRIVATE_KEY_BEGINNING)
+            key_end = data.find(PEM_PRIVATE_KEY_ENDING)
+
+            if key_start == -1:
+                # Did not find the start of private key.
+
+                if data.find('-----BEGIN PUBLIC KEY-----') != -1 or \
+                   data.find('-----BEGIN RSA PUBLIC KEY-----') != -1 or \
+                   data.find('ssh-rsa ') != -1 or \
+                   data.find('---- BEGIN SSH2 PUBLIC KEY ----') != -1:
+                    # Appears to contain a PKCS8, PEM, OpenSSH old or
+                    # OpenSSH new format public key.
+                    # The newer OpenSSH format does not follow RFC7468
+                    # and only has 4 hyphens and spaces around the text!
+                    err = 'wrong key, please provide the PRIVATE key'
+                elif data.find('-----BEGIN OPENSSH PRIVATE KEY-----') != -1:
+                    # Appears to contain newer OpenSSH private key format
+                    err = 'private key format not supported' + \
+                          ', PEM format required'
+                else:
+                    # Generic error message
+                    err = 'does not contain a PEM formatted private key'
+
+            else:
+                if key_end == -1:
+                    err = 'private key is incomplete'
+                else:
+                    key_end += len(PEM_PRIVATE_KEY_ENDING)
+                    err = None
+
+            # If the username is blank, try to extract a username from the file
+
+            if len(username) == 0 and err is None:
+                username, err = OAuth1Plugin.extract_username(data, ATTR_NAME,
+                                                              0, key_start)
+
+            if err is not None:
+                sys.stderr.write("http: " + filename + ': ' + err)
+                sys.exit(1)
+
+            pem_key = data[key_start:key_end]
+
+            return username, pem_key
+
+        except IOError as e:
+            sys.stderr.write("http: " + str(e))
+            sys.exit(1)
+
+    @staticmethod
+    def extract_username(data, attr_name, start, end, limit=8096):
+        """
+        Extract a named parameter from the contents.
+
+        :param data: text to search
+        :param attr_name: name of attribute to look for
+        :param start: index into contents of where to start looking
+        :param end: index into contents of where to stop looking
+        :param limit: upper limit for end position
+        :return: client-key value or None if not found
+        """
+        stop_pos = end
+        if limit < end:
+            stop_pos = limit
+        i = start
+
+        while i < stop_pos:
+            eol_pos = data.find('\n', i, stop_pos)
+            if eol_pos == -1:
+                break  # no more complete lines found
+
+            colon_pos = data.find(':', i, eol_pos)
+            if colon_pos != -1:
+                name = data[i:colon_pos].strip()
+                value = data[colon_pos + 1: eol_pos].strip()
+                if name == attr_name:
+                    return value, None  # successfully found
+            i = eol_pos + 1
 
-    def get_auth(self, username, password):
-        return OAuth1(client_key=username, client_secret=password)
+        if limit < end:
+            return None, '"{}" not found in first {} characters'.format(
+                         attr_name, limit)
+        else:
+            return None, '"{}" not found before private key'.format(attr_name)
diff --git a/setup.py b/setup.py
index 33f58f8..2d779d2 100644
--- a/setup.py
+++ b/setup.py
@@ -9,7 +9,7 @@
     name='httpie-oauth',
     description='OAuth plugin for HTTPie.',
     long_description=open('README.rst').read().strip(),
-    version='1.0.2',
+    version='2.0.0',
     author='Jakub Roztocil',
     author_email='jakub@roztocil.name',
     license='BSD',