text: // Copyright Joyent, Inc. and other Node contributors.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a
  // copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to permit
  // persons to whom the Software is furnished to do so, subject to the
  // following conditions:
  //
  // The above copyright notice and this permission notice shall be included
  // in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  // USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  // Note: In 0.8 and before, crypto functions all defaulted to using
  // binary-encoded strings rather than buffers.
  
  exports.DEFAULT_ENCODING = 'buffer';
  
  try {
    var binding = process.binding('crypto');
    var SecureContext = binding.SecureContext;
    var randomBytes = binding.randomBytes;
    var pseudoRandomBytes = binding.pseudoRandomBytes;
    var getCiphers = binding.getCiphers;
    var getHashes = binding.getHashes;
  } catch (e) {
    throw new Error('node.js not compiled with openssl crypto support.');
  }
  
  var stream = require('stream');
  var util = require('util');
  
  // This is here because many functions accepted binary strings without
  // any explicit encoding in older versions of node, and we don't want
  // to break them unnecessarily.
  function toBuf(str, encoding) {
    encoding = encoding || 'binary';
    if (IS_STRING(str)) {
      if (encoding === 'buffer')
        encoding = 'binary';
      str = new Buffer(str, encoding);
    }
    return str;
  }
  
  
  var assert = require('assert');
  var StringDecoder = require('string_decoder').StringDecoder;
  
  function Credentials(secureProtocol, flags, context) {
    if (!(this instanceof Credentials)) {
      return new Credentials(secureProtocol, flags, context);
    }
  
    if (context) {
      this.context = context;
    } else {
      this.context = new SecureContext();
  
      if (secureProtocol) {
        this.context.init(secureProtocol);
      } else {
        this.context.init();
      }
    }
  
    if (flags) this.context.setOptions(flags);
  }
  
  exports.Credentials = Credentials;
  
  
  exports.createCredentials = function(options, context) {
    if (!options) options = {};
  
    var c = new Credentials(options.secureProtocol,
                            options.secureOptions,
                            context);
  
    if (context) return c;
  
    if (options.key) {
      if (options.passphrase) {
        c.context.setKey(options.key, options.passphrase);
      } else {
        c.context.setKey(options.key);
      }
    }
  
    if (options.cert) c.context.setCert(options.cert);
  
    if (options.ciphers) c.context.setCiphers(options.ciphers);
  
    if (options.ca) {
      if (IS_ARRAY(options.ca)) {
        for (var i = 0, len = options.ca.length; i < len; i++) {
          c.context.addCACert(options.ca[i]);
        }
      } else {
        c.context.addCACert(options.ca);
      }
    } else {
      c.context.addRootCerts();
    }
  
    if (options.crl) {
      if (IS_ARRAY(options.crl)) {
        for (var i = 0, len = options.crl.length; i < len; i++) {
          c.context.addCRL(options.crl[i]);
        }
      } else {
        c.context.addCRL(options.crl);
      }
    }
  
    if (options.sessionIdContext) {
      c.context.setSessionIdContext(options.sessionIdContext);
    }
  
    if (options.pfx) {
      var pfx = options.pfx;
      var passphrase = options.passphrase;
  
      pfx = toBuf(pfx);
      if (passphrase)
        passphrase = toBuf(passphrase);
  
      if (passphrase) {
        c.context.loadPKCS12(pfx, passphrase);
      } else {
        c.context.loadPKCS12(pfx);
      }
    }
  
    return c;
  };
  
  
  function LazyTransform(options) {
    this._options = options;
  }
  util.inherits(LazyTransform, stream.Transform);
  
  [
    '_readableState',
    '_writableState',
    '_transformState'
  ].forEach(function(prop, i, props) {
    Object.defineProperty(LazyTransform.prototype, prop, {
      get: function() {
        stream.Transform.call(this, this._options);
        this._writableState.decodeStrings = false;
        this._writableState.defaultEncoding = 'binary';
        return this[prop];
      },
      set: function(val) {
        Object.defineProperty(this, prop, {
          value: val,
          enumerable: true,
          configurable: true,
          writable: true
        });
      },
      configurable: true,
      enumerable: true
    });
  });
  
  
  exports.createHash = exports.Hash = Hash;
  function Hash(algorithm, options) {
    if (!(this instanceof Hash))
      return new Hash(algorithm, options);
    this._binding = new binding.Hash(algorithm);
    LazyTransform.call(this, options);
  }
  
  util.inherits(Hash, LazyTransform);
  
  Hash.prototype._transform = function(chunk, encoding, callback) {
    this._binding.update(chunk, encoding);
    callback();
  };
  
  Hash.prototype._flush = function(callback) {
    var encoding = this._readableState.encoding || 'buffer';
    this.push(this._binding.digest(encoding), encoding);
    callback();
  };
  
  Hash.prototype.update = function(data, encoding) {
    encoding = encoding || exports.DEFAULT_ENCODING;
    if (encoding === 'buffer' && IS_STRING(data))
      encoding = 'binary';
    this._binding.update(data, encoding);
    return this;
  };
  
  
  Hash.prototype.digest = function(outputEncoding) {
    outputEncoding = outputEncoding || exports.DEFAULT_ENCODING;
    return this._binding.digest(outputEncoding);
  };
  
  
  exports.createHmac = exports.Hmac = Hmac;
  
  function Hmac(hmac, key, options) {
    if (!(this instanceof Hmac))
      return new Hmac(hmac, key, options);
    this._binding = new binding.Hmac();
    this._binding.init(hmac, toBuf(key));
    LazyTransform.call(this, options);
  }
  
  util.inherits(Hmac, LazyTransform);
  
  Hmac.prototype.update = Hash.prototype.update;
  Hmac.prototype.digest = Hash.prototype.digest;
  Hmac.prototype._flush = Hash.prototype._flush;
  Hmac.prototype._transform = Hash.prototype._transform;
  
  
  function getDecoder(decoder, encoding) {
    if (encoding === 'utf-8') encoding = 'utf8';  // Normalize encoding.
    decoder = decoder || new StringDecoder(encoding);
    assert(decoder.encoding === encoding, 'Cannot change encoding');
    return decoder;
  }
  
  
  exports.createCipher = exports.Cipher = Cipher;
  function Cipher(cipher, password, options) {
    if (!(this instanceof Cipher))
      return new Cipher(cipher, password, options);
    this._binding = new binding.CipherBase(true);
  
    this._binding.init(cipher, toBuf(password));
    this._decoder = null;
  
    LazyTransform.call(this, options);
  }
  
  util.inherits(Cipher, LazyTransform);
  
  Cipher.prototype._transform = function(chunk, encoding, callback) {
    this.push(this._binding.update(chunk, encoding));
    callback();
  };
  
  Cipher.prototype._flush = function(callback) {
    this.push(this._binding.final());
    callback();
  };
  
  Cipher.prototype.update = function(data, inputEncoding, outputEncoding) {
    inputEncoding = inputEncoding || exports.DEFAULT_ENCODING;
    outputEncoding = outputEncoding || exports.DEFAULT_ENCODING;
  
    var ret = this._binding.update(data, inputEncoding);
  
    if (outputEncoding && outputEncoding !== 'buffer') {
      this._decoder = getDecoder(this._decoder, outputEncoding);
      ret = this._decoder.write(ret);
    }
  
    return ret;
  };
  
  
  Cipher.prototype.final = function(outputEncoding) {
    outputEncoding = outputEncoding || exports.DEFAULT_ENCODING;
    var ret = this._binding.final();
  
    if (outputEncoding && outputEncoding !== 'buffer') {
      this._decoder = getDecoder(this._decoder, outputEncoding);
      ret = this._decoder.end(ret);
    }
  
    return ret;
  };
  
  
  Cipher.prototype.setAutoPadding = function(ap) {
    this._binding.setAutoPadding(ap);
    return this;
  };
  
  
  
  exports.createCipheriv = exports.Cipheriv = Cipheriv;
  function Cipheriv(cipher, key, iv, options) {
    if (!(this instanceof Cipheriv))
      return new Cipheriv(cipher, key, iv, options);
    this._binding = new binding.CipherBase(true);
    this._binding.initiv(cipher, toBuf(key), toBuf(iv));
    this._decoder = null;
  
    LazyTransform.call(this, options);
  }
  
  util.inherits(Cipheriv, LazyTransform);
  
  Cipheriv.prototype._transform = Cipher.prototype._transform;
  Cipheriv.prototype._flush = Cipher.prototype._flush;
  Cipheriv.prototype.update = Cipher.prototype.update;
  Cipheriv.prototype.final = Cipher.prototype.final;
  Cipheriv.prototype.setAutoPadding = Cipher.prototype.setAutoPadding;
  
  
  
  exports.createDecipher = exports.Decipher = Decipher;
  function Decipher(cipher, password, options) {
    if (!(this instanceof Decipher))
      return new Decipher(cipher, password, options);
  
    this._binding = new binding.CipherBase(false);
    this._binding.init(cipher, toBuf(password));
    this._decoder = null;
  
    LazyTransform.call(this, options);
  }
  
  util.inherits(Decipher, LazyTransform);
  
  Decipher.prototype._transform = Cipher.prototype._transform;
  Decipher.prototype._flush = Cipher.prototype._flush;
  Decipher.prototype.update = Cipher.prototype.update;
  Decipher.prototype.final = Cipher.prototype.final;
  Decipher.prototype.finaltol = Cipher.prototype.final;
  Decipher.prototype.setAutoPadding = Cipher.prototype.setAutoPadding;
  
  
  
  exports.createDecipheriv = exports.Decipheriv = Decipheriv;
  function Decipheriv(cipher, key, iv, options) {
    if (!(this instanceof Decipheriv))
      return new Decipheriv(cipher, key, iv, options);
  
    this._binding = new binding.CipherBase(false);
    this._binding.initiv(cipher, toBuf(key), toBuf(iv));
    this._decoder = null;
  
    LazyTransform.call(this, options);
  }
  
  util.inherits(Decipheriv, LazyTransform);
  
  Decipheriv.prototype._transform = Cipher.prototype._transform;
  Decipheriv.prototype._flush = Cipher.prototype._flush;
  Decipheriv.prototype.update = Cipher.prototype.update;
  Decipheriv.prototype.final = Cipher.prototype.final;
  Decipheriv.prototype.finaltol = Cipher.prototype.final;
  Decipheriv.prototype.setAutoPadding = Cipher.prototype.setAutoPadding;
  
  
  
  exports.createSign = exports.Sign = Sign;
  function Sign(algorithm, options) {
    if (!(this instanceof Sign))
      return new Sign(algorithm, options);
    this._binding = new binding.Sign();
    this._binding.init(algorithm);
  
    stream.Writable.call(this, options);
  }
  
  util.inherits(Sign, stream.Writable);
  
  Sign.prototype._write = function(chunk, encoding, callback) {
    this._binding.update(chunk, encoding);
    callback();
  };
  
  Sign.prototype.update = Hash.prototype.update;
  
  Sign.prototype.sign = function(key, encoding) {
    encoding = encoding || exports.DEFAULT_ENCODING;
    var ret = this._binding.sign(toBuf(key));
  
    if (encoding && encoding !== 'buffer')
      ret = ret.toString(encoding);
  
    return ret;
  };
  
  
  
  exports.createVerify = exports.Verify = Verify;
  function Verify(algorithm, options) {
    if (!(this instanceof Verify))
      return new Verify(algorithm, options);
  
    this._binding = new binding.Verify;
    this._binding.init(algorithm);
  
    stream.Writable.call(this, options);
  }
  
  util.inherits(Verify, stream.Writable);
  
  Verify.prototype._write = Sign.prototype._write;
  Verify.prototype.update = Sign.prototype.update;
  
  Verify.prototype.verify = function(object, signature, sigEncoding) {
    sigEncoding = sigEncoding || exports.DEFAULT_ENCODING;
    return this._binding.verify(toBuf(object), toBuf(signature, sigEncoding));
  };
  
  
  
  exports.createDiffieHellman = exports.DiffieHellman = DiffieHellman;
  
  function DiffieHellman(sizeOrKey, encoding) {
    if (!(this instanceof DiffieHellman))
      return new DiffieHellman(sizeOrKey, encoding);
  
    if (!sizeOrKey)
      this._binding = new binding.DiffieHellman();
    else {
      encoding = encoding || exports.DEFAULT_ENCODING;
      sizeOrKey = toBuf(sizeOrKey, encoding);
      this._binding = new binding.DiffieHellman(sizeOrKey);
    }
  }
  
  
  exports.DiffieHellmanGroup =
      exports.createDiffieHellmanGroup =
      exports.getDiffieHellman = DiffieHellmanGroup;
  
  function DiffieHellmanGroup(name) {
    if (!(this instanceof DiffieHellmanGroup))
      return new DiffieHellmanGroup(name);
    this._binding = new binding.DiffieHellmanGroup(name);
  }
  
  
  DiffieHellmanGroup.prototype.generateKeys =
      DiffieHellman.prototype.generateKeys =
      dhGenerateKeys;
  
  function dhGenerateKeys(encoding) {
    var keys = this._binding.generateKeys();
    encoding = encoding || exports.DEFAULT_ENCODING;
    if (encoding && encoding !== 'buffer')
      keys = keys.toString(encoding);
    return keys;
  }
  
  
  DiffieHellmanGroup.prototype.computeSecret =
      DiffieHellman.prototype.computeSecret =
      dhComputeSecret;
  
  function dhComputeSecret(key, inEnc, outEnc) {
    inEnc = inEnc || exports.DEFAULT_ENCODING;
    outEnc = outEnc || exports.DEFAULT_ENCODING;
    var ret = this._binding.computeSecret(toBuf(key, inEnc));
    if (outEnc && outEnc !== 'buffer')
      ret = ret.toString(outEnc);
    return ret;
  }
  
  
  DiffieHellmanGroup.prototype.getPrime =
      DiffieHellman.prototype.getPrime =
      dhGetPrime;
  
  function dhGetPrime(encoding) {
    var prime = this._binding.getPrime();
    encoding = encoding || exports.DEFAULT_ENCODING;
    if (encoding && encoding !== 'buffer')
      prime = prime.toString(encoding);
    return prime;
  }
  
  
  DiffieHellmanGroup.prototype.getGenerator =
      DiffieHellman.prototype.getGenerator =
      dhGetGenerator;
  
  function dhGetGenerator(encoding) {
    var generator = this._binding.getGenerator();
    encoding = encoding || exports.DEFAULT_ENCODING;
    if (encoding && encoding !== 'buffer')
      generator = generator.toString(encoding);
    return generator;
  }
  
  
  DiffieHellmanGroup.prototype.getPublicKey =
      DiffieHellman.prototype.getPublicKey =
      dhGetPublicKey;
  
  function dhGetPublicKey(encoding) {
    var key = this._binding.getPublicKey();
    encoding = encoding || exports.DEFAULT_ENCODING;
    if (encoding && encoding !== 'buffer')
      key = key.toString(encoding);
    return key;
  }
  
  
  DiffieHellmanGroup.prototype.getPrivateKey =
      DiffieHellman.prototype.getPrivateKey =
      dhGetPrivateKey;
  
  function dhGetPrivateKey(encoding) {
    var key = this._binding.getPrivateKey();
    encoding = encoding || exports.DEFAULT_ENCODING;
    if (encoding && encoding !== 'buffer')
      key = key.toString(encoding);
    return key;
  }
  
  
  DiffieHellman.prototype.setPublicKey = function(key, encoding) {
    encoding = encoding || exports.DEFAULT_ENCODING;
    this._binding.setPublicKey(toBuf(key, encoding));
    return this;
  };
  
  
  DiffieHellman.prototype.setPrivateKey = function(key, encoding) {
    encoding = encoding || exports.DEFAULT_ENCODING;
    this._binding.setPrivateKey(toBuf(key, encoding));
    return this;
  };
  
  
  
  exports.pbkdf2 = function(password, salt, iterations, keylen, callback) {
    if (!IS_FUNCTION(callback))
      throw new Error('No callback provided to pbkdf2');
  
    return pbkdf2(password, salt, iterations, keylen, callback);
  };
  
  
  exports.pbkdf2Sync = function(password, salt, iterations, keylen) {
    return pbkdf2(password, salt, iterations, keylen);
  };
  
  
  function pbkdf2(password, salt, iterations, keylen, callback) {
    password = toBuf(password);
    salt = toBuf(salt);
  
    if (exports.DEFAULT_ENCODING === 'buffer')
      return binding.PBKDF2(password, salt, iterations, keylen, callback);
  
    // at this point, we need to handle encodings.
    var encoding = exports.DEFAULT_ENCODING;
    if (callback) {
      binding.PBKDF2(password, salt, iterations, keylen, function(er, ret) {
        if (ret)
          ret = ret.toString(encoding);
        callback(er, ret);
      });
    } else {
      var ret = binding.PBKDF2(password, salt, iterations, keylen);
      return ret.toString(encoding);
    }
  }
  
  
  
  exports.randomBytes = randomBytes;
  exports.pseudoRandomBytes = pseudoRandomBytes;
  
  exports.rng = randomBytes;
  exports.prng = pseudoRandomBytes;
  
  
  exports.getCiphers = function() {
    return filterDuplicates(getCiphers.call(null, arguments));
  };
  
  
  exports.getHashes = function() {
    return filterDuplicates(getHashes.call(null, arguments));
  
  };
  
  
  function filterDuplicates(names) {
    // Drop all-caps names in favor of their lowercase aliases,
    // for example, 'sha1' instead of 'SHA1'.
    var ctx = {};
    names.forEach(function(name) {
      if (/^[0-9A-Z\-]+$/.test(name)) name = name.toLowerCase();
      ctx[name] = true;
    });
    return Object.getOwnPropertyNames(ctx).sort();
  }
  