用eccrypto加解密，用crypto签名。互相转换压缩和非压缩公钥

test-decompress.js

@@ -0,0 +1,38 @@
+const bigInt = require("big-integer");
+
+// Consts for P256 curve. Adjust accordingly
+const two = new bigInt(2),
+// 115792089210356248762697446949407573530086143415290314195533631308867097853951
+prime = two.pow(256).subtract( two.pow(224) ).add( two.pow(192) ).add( two.pow(96) ).subtract(1),
+b = new bigInt( '41058363725152142129326129780047268409114441015993725554835256314039467401291' ),
+// Pre-computed value, or literal
+// 28948022302589062190674361737351893382521535853822578548883407827216774463488
+pIdent = prime.add(1).divide(4);
+
+function pad_with_zeroes(number, length) {
+    var retval = '' + number;
+    while (retval.length < length) {
+        retval = '0' + retval;
+    }
+    return retval;
+}
+
+/**
+ * Point decompress NIST curve
+ * @param {string} Compressed representation in hex string
+ * @return {string} Uncompressed representation in hex string
+ */
+function ECPointDecompress( comp ) {
+    var signY = new Number(comp[1]) - 2;
+    var x = new bigInt(comp.substring(2), 16);
+    // y^2 = x^3 - 3x + b
+    var y = x.pow(3).subtract( x.multiply(3) ).add( b ).modPow( pIdent, prime );
+    // If the parity doesn't match it's the *other* root
+    if( y.mod(2).toJSNumber() !== signY ) {
+        // y = prime - y
+        y = prime.subtract( y );
+    }
+    return '04' + pad_with_zeroes(x.toString(16), 64) + pad_with_zeroes(y.toString(16), 64);
+}
+
+console.log(ECPointDecompress('035d77c1e3eac37f685aeea2ae872c4e7e4d159756e57601db3bcccbc549f360b2'))