diff --git a/index.html b/index.html
index 6ff4303..e317f06 100644
--- a/index.html
+++ b/index.html
@@ -84,7 +84,7 @@
 	<script type="text/javascript" src="https://code.jquery.com/jquery-1.12.0.min.js"></script>
 
 
-	 <script type="text/javascript" src="https://rawcdn.githack.com/chrisveness/crypto/7067ee62f18c76dd4a9d372a00e647205460b62b/sha1.js"></script>
+	 <script type="text/javascript" src="sha1.js"></script>
 
 	<script type="text/javascript">
 	"use strict";
diff --git a/sha1.js b/sha1.js
new file mode 100644
index 0000000..08b06ea
--- /dev/null
+++ b/sha1.js
@@ -0,0 +1,158 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
+/* SHA-1 (FIPS 180-4) implementation in JavaScript                    (c) Chris Veness 2002-2019  */
+/*                                                                                   MIT Licence  */
+/* www.movable-type.co.uk/scripts/sha1.html                                                       */
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
+
+
+/**
+ * SHA-1 hash function reference implementation.
+ *
+ * This is an annotated direct implementation of FIPS 180-4, without any optimisations. It is
+ * intended to aid understanding of the algorithm rather than for production use.
+ *
+ * While it could be used where performance is not critical, I would recommend using the ‘Web
+ * Cryptography API’ (developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/digest) for the browser,
+ * or the ‘crypto’ library (nodejs.org/api/crypto.html#crypto_class_hash) in Node.js.
+ *
+ * See csrc.nist.gov/groups/ST/toolkit/secure_hashing.html
+ *     csrc.nist.gov/groups/ST/toolkit/examples.html
+ */
+class Sha1 {
+
+    /**
+     * Generates SHA-1 hash of string.
+     *
+     * @param   {string} msg - (Unicode) string to be hashed.
+     * @param   {Object} [options]
+     * @param   {string} [options.msgFormat=string] - Message format: 'string' for JavaScript string
+     *   (gets converted to UTF-8 for hashing); 'hex-bytes' for string of hex bytes ('616263' ≡ 'abc') .
+     * @param   {string} [options.outFormat=hex] - Output format: 'hex' for string of contiguous
+     *   hex bytes; 'hex-w' for grouping hex bytes into groups of (4 byte / 8 character) words.
+     * @returns {string} Hash of msg as hex character string.
+     *
+     * @example
+     *   import Sha1 from './sha1.js';
+     *   const hash = Sha1.hash('abc'); // 'a9993e364706816aba3e25717850c26c9cd0d89d'
+     */
+    static hash(msg, options) {
+        const defaults = { msgFormat: 'string', outFormat: 'hex' };
+        const opt = Object.assign(defaults, options);
+
+        switch (opt.msgFormat) {
+            default: // default is to convert string to UTF-8, as SHA only deals with byte-streams
+            case 'string':   msg = utf8Encode(msg);       break;
+            case 'hex-bytes':msg = hexBytesToString(msg); break; // mostly for running tests
+        }
+
+        // constants [§4.2.1]
+        const K = [ 0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6 ];
+
+        // initial hash value [§5.3.1]
+        const H = [ 0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0 ];
+
+        // PREPROCESSING [§6.1.1]
+
+        msg += String.fromCharCode(0x80);  // add trailing '1' bit (+ 0's padding) to string [§5.1.1]
+
+        // convert string msg into 512-bit/16-integer blocks arrays of ints [§5.2.1]
+        const l = msg.length/4 + 2; // length (in 32-bit integers) of msg + ‘1’ + appended length
+        const N = Math.ceil(l/16);  // number of 16-integer-blocks required to hold 'l' ints
+        const M = new Array(N);
+
+        for (let i=0; i<N; i++) {
+            M[i] = new Array(16);
+            for (let j=0; j<16; j++) {  // encode 4 chars per integer, big-endian encoding
+                M[i][j] = (msg.charCodeAt(i*64+j*4+0)<<24) | (msg.charCodeAt(i*64+j*4+1)<<16)
+                        | (msg.charCodeAt(i*64+j*4+2)<< 8) | (msg.charCodeAt(i*64+j*4+3)<< 0);
+            } // note running off the end of msg is ok 'cos bitwise ops on NaN return 0
+        }
+        // add length (in bits) into final pair of 32-bit integers (big-endian) [§5.1.1]
+        // note: most significant word would be (len-1)*8 >>> 32, but since JS converts
+        // bitwise-op args to 32 bits, we need to simulate this by arithmetic operators
+        M[N-1][14] = ((msg.length-1)*8) / Math.pow(2, 32); M[N-1][14] = Math.floor(M[N-1][14]);
+        M[N-1][15] = ((msg.length-1)*8) & 0xffffffff;
+
+        // HASH COMPUTATION [§6.1.2]
+
+        for (let i=0; i<N; i++) {
+            const W = new Array(80);
+
+            // 1 - prepare message schedule 'W'
+            for (let t=0;  t<16; t++) W[t] = M[i][t];
+            for (let t=16; t<80; t++) W[t] = Sha1.ROTL(W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1);
+
+            // 2 - initialise five working variables a, b, c, d, e with previous hash value
+            let a = H[0], b = H[1], c = H[2], d = H[3], e = H[4];
+
+            // 3 - main loop (use JavaScript '>>> 0' to emulate UInt32 variables)
+            for (let t=0; t<80; t++) {
+                const s = Math.floor(t/20); // seq for blocks of 'f' functions and 'K' constants
+                const T = (Sha1.ROTL(a, 5) + Sha1.f(s, b, c, d) + e + K[s] + W[t]) >>> 0;
+                e = d;
+                d = c;
+                c = Sha1.ROTL(b, 30) >>> 0;
+                b = a;
+                a = T;
+            }
+
+            // 4 - compute the new intermediate hash value (note 'addition modulo 2^32' – JavaScript
+            // '>>> 0' coerces to unsigned UInt32 which achieves modulo 2^32 addition)
+            H[0] = (H[0]+a) >>> 0;
+            H[1] = (H[1]+b) >>> 0;
+            H[2] = (H[2]+c) >>> 0;
+            H[3] = (H[3]+d) >>> 0;
+            H[4] = (H[4]+e) >>> 0;
+        }
+
+        // convert H0..H4 to hex strings (with leading zeros)
+        for (let h=0; h<H.length; h++) H[h] = ('00000000'+H[h].toString(16)).slice(-8);
+
+        // concatenate H0..H4, with separator if required
+        const separator = opt.outFormat=='hex-w' ? ' ' : '';
+
+        return H.join(separator);
+
+        /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
+
+        function utf8Encode(str) {
+            try {
+                return new TextEncoder().encode(str, 'utf-8').reduce((prev, curr) => prev + String.fromCharCode(curr), '');
+            } catch (e) { // no TextEncoder available?
+                return unescape(encodeURIComponent(str)); // monsur.hossa.in/2012/07/20/utf-8-in-javascript.html
+            }
+        }
+
+        function hexBytesToString(hexStr) { // convert string of hex numbers to a string of chars (eg '616263' -> 'abc').
+            const str = hexStr.replace(' ', ''); // allow space-separated groups
+            return str=='' ? '' : str.match(/.{2}/g).map(byte => String.fromCharCode(parseInt(byte, 16))).join('');
+        }
+    }
+
+
+    /**
+     * Function 'f' [§4.1.1].
+     * @private
+     */
+    static f(s, x, y, z)  {
+        switch (s) {
+            case 0: return (x & y) ^ (~x & z);          // Ch()
+            case 1: return  x ^ y  ^  z;                // Parity()
+            case 2: return (x & y) ^ (x & z) ^ (y & z); // Maj()
+            case 3: return  x ^ y  ^  z;                // Parity()
+        }
+    }
+
+
+    /**
+     * Rotates left (circular left shift) value x by n positions [§3.2.5].
+     * @private
+     */
+    static ROTL(x, n) {
+        return (x<<n) | (x>>>(32-n));
+    }
+
+}
+
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */