diff --git a/README.md b/README.md
index 6f514c1..d8c60c2 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,8 @@ Do nostr stuff with Clojure.
 
 Heavy WIP. At this point it probably won't make much sense too you.
 
+You might have to run `javac -d java $(find java -name "*.java")` 
+
 ## Usage
 
 FIXME: write usage documentation!
diff --git a/deps.edn b/deps.edn
index a8fec88..9ecb67b 100644
--- a/deps.edn
+++ b/deps.edn
@@ -1,4 +1,4 @@
-{:paths ["src" "resources"]
+{:paths ["src" "resources" "java"]
  :deps {org.clojure/clojure {:mvn/version "1.12.0"}
         cheshire/cheshire {:mvn/version "5.13.0"}
         hato/hato {:mvn/version "1.0.0"}}
diff --git a/java/schnorr/Main.java b/java/schnorr/Main.java
new file mode 100644
index 0000000..e40b2c4
--- /dev/null
+++ b/java/schnorr/Main.java
@@ -0,0 +1,128 @@
+package schnorr;
+
+import java.util.Arrays;
+
+public class Main {
+
+    public static void main(String[] args) {
+
+        String[] data =  {
+                // index,secret key,public key, aux rand, message,signature,verification result,comment
+                "0,0000000000000000000000000000000000000000000000000000000000000003,F9308A019258C31049344F85F89D5229B531C845836F99B08601F113BCE036F9,0000000000000000000000000000000000000000000000000000000000000000,0000000000000000000000000000000000000000000000000000000000000000,E907831F80848D1069A5371B402410364BDF1C5F8307B0084C55F1CE2DCA821525F66A4A85EA8B71E482A74F382D2CE5EBEEE8FDB2172F477DF4900D310536C0,TRUE",
+                "1,B7E151628AED2A6ABF7158809CF4F3C762E7160F38B4DA56A784D9045190CFEF,DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659,0000000000000000000000000000000000000000000000000000000000000001,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,6896BD60EEAE296DB48A229FF71DFE071BDE413E6D43F917DC8DCF8C78DE33418906D11AC976ABCCB20B091292BFF4EA897EFCB639EA871CFA95F6DE339E4B0A,TRUE",
+                "2,C90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B14E5C9,DD308AFEC5777E13121FA72B9CC1B7CC0139715309B086C960E18FD969774EB8,C87AA53824B4D7AE2EB035A2B5BBBCCC080E76CDC6D1692C4B0B62D798E6D906,7E2D58D8B3BCDF1ABADEC7829054F90DDA9805AAB56C77333024B9D0A508B75C,5831AAEED7B44BB74E5EAB94BA9D4294C49BCF2A60728D8B4C200F50DD313C1BAB745879A5AD954A72C45A91C3A51D3C7ADEA98D82F8481E0E1E03674A6F3FB7,TRUE",
+                "3,0B432B2677937381AEF05BB02A66ECD012773062CF3FA2549E44F58ED2401710,25D1DFF95105F5253C4022F628A996AD3A0D95FBF21D468A1B33F8C160D8F517,FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF,FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF,7EB0509757E246F19449885651611CB965ECC1A187DD51B64FDA1EDC9637D5EC97582B9CB13DB3933705B32BA982AF5AF25FD78881EBB32771FC5922EFC66EA3,TRUE,test fails if msg is reduced modulo p or n",
+                "4,,D69C3509BB99E412E68B0FE8544E72837DFA30746D8BE2AA65975F29D22DC7B9,,4DF3C3F68FCC83B27E9D42C90431A72499F17875C81A599B566C9889B9696703,00000000000000000000003B78CE563F89A0ED9414F5AA28AD0D96D6795F9C6376AFB1548AF603B3EB45C9F8207DEE1060CB71C04E80F593060B07D28308D7F4,TRUE",
+                "5,,EEFDEA4CDB677750A420FEE807EACF21EB9898AE79B9768766E4FAA04A2D4A34,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,6CFF5C3BA86C69EA4B7376F31A9BCB4F74C1976089B2D9963DA2E5543E17776969E89B4C5564D00349106B8497785DD7D1D713A8AE82B32FA79D5F7FC407D39B,FALSE,public key not on the curve",
+                "6,,DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,FFF97BD5755EEEA420453A14355235D382F6472F8568A18B2F057A14602975563CC27944640AC607CD107AE10923D9EF7A73C643E166BE5EBEAFA34B1AC553E2,FALSE,has_even_y(R) is false",
+                "7,,DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,1FA62E331EDBC21C394792D2AB1100A7B432B013DF3F6FF4F99FCB33E0E1515F28890B3EDB6E7189B630448B515CE4F8622A954CFE545735AAEA5134FCCDB2BD,FALSE,negated message",
+                "8,,DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,6CFF5C3BA86C69EA4B7376F31A9BCB4F74C1976089B2D9963DA2E5543E177769961764B3AA9B2FFCB6EF947B6887A226E8D7C93E00C5ED0C1834FF0D0C2E6DA6,FALSE,negated s value",
+                "9,,DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,0000000000000000000000000000000000000000000000000000000000000000123DDA8328AF9C23A94C1FEECFD123BA4FB73476F0D594DCB65C6425BD186051,FALSE,sG - eP is infinite. Test fails in single verification if has_even_y(inf) is defined as true and x(inf) as 0",
+                "10,,DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,00000000000000000000000000000000000000000000000000000000000000017615FBAF5AE28864013C099742DEADB4DBA87F11AC6754F93780D5A1837CF197,FALSE,sG - eP is infinite. Test fails in single verification if has_even_y(inf) is defined as true and x(inf) as 1",
+                "11,,DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,4A298DACAE57395A15D0795DDBFD1DCB564DA82B0F269BC70A74F8220429BA1D69E89B4C5564D00349106B8497785DD7D1D713A8AE82B32FA79D5F7FC407D39B,FALSE,sig[0:32] is not an X coordinate on the curve",
+                "12,,DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F69E89B4C5564D00349106B8497785DD7D1D713A8AE82B32FA79D5F7FC407D39B,FALSE,sig[0:32] is equal to field size",
+                "13,,DFF1D77F2A671C5F36183726DB2341BE58FEAE1DA2DECED843240F7B502BA659,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,6CFF5C3BA86C69EA4B7376F31A9BCB4F74C1976089B2D9963DA2E5543E177769FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141,FALSE,sig[32:64] is equal to curve order",
+                "14,,FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC30,,243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89,6CFF5C3BA86C69EA4B7376F31A9BCB4F74C1976089B2D9963DA2E5543E17776969E89B4C5564D00349106B8497785DD7D1D713A8AE82B32FA79D5F7FC407D39B,FALSE,public key is not a valid X coordinate because it exceeds the field size",
+        };
+
+        boolean allSigsPassed = true;
+        boolean allVerifsPassed = true;
+
+        for(int i = 0; i < data.length; i++)   {
+            String[] s = data[i].split(",");
+            String index = s[0];
+            String seckey = s[1];
+            String pubkey = s[2];
+            String auxrand = s[3];
+            String msg = s[4];
+            String sig = s[5];
+            String result = s[6];
+            String comment = (s.length == 8) ? s[7] : null;
+
+            byte[] _pubkey = Util.hexToBytes(pubkey);
+            byte[] _auxrand = Util.hexToBytes(auxrand);
+            byte[] _msg = Util.hexToBytes(msg);
+            byte[] _sig = Util.hexToBytes(sig);
+            boolean _result = result.equals("TRUE");
+
+            System.out.println("\nTest vector:" + Integer.valueOf(index));
+
+            if(seckey != null && seckey.length() > 0)   {
+                byte[] _seckey = Util.hexToBytes(seckey);
+                try   {
+                    byte[] _pubkeyActual = Point.genPubKey(_seckey);
+                    if(!Arrays.equals(_pubkey, _pubkeyActual))   {
+                        System.out.println(" * Failed key generation.");
+                        System.out.println("\tExpected key:" + Util.bytesToHex(_pubkey));
+                        System.out.println("\tActual key:" + Util.bytesToHex(_pubkeyActual));
+
+                        allSigsPassed = false;
+                    }
+                }
+                catch(Exception e)   {
+                    System.out.println(e.getMessage());
+                }
+                try   {
+                    byte[] _sigActual = Schnorr.sign(_msg, _seckey, _auxrand);
+
+                    if(Arrays.equals(_sig, _sigActual))   {
+                        System.out.println(" * Passed signing test.");
+                    }
+                    else   {
+                        System.out.println(" * Failed signing test.");
+                        System.out.println("\tExpected signature:" + Util.bytesToHex(_sig));
+                        System.out.println("\tActual signature:" + Util.bytesToHex(_sigActual));
+
+                        allSigsPassed = false;
+                    }
+
+                }
+                catch(Exception e)   {
+                    System.out.println(e.getMessage());
+                    allSigsPassed = false;
+                }
+
+            }
+
+            try   {
+                boolean resultActual = Schnorr.verify(_msg, _pubkey, _sig);
+
+                if(_result == resultActual)   {
+                    System.out.println(" * Passed verification test.");
+                }
+                else   {
+                    System.out.println(" * Failed verification test.");
+                    System.out.println("\tExpected verification result:" + result);
+                    System.out.println("\tActual verification result:" + resultActual);
+
+                    if(comment != null)   {
+                        System.out.println("\tComment:" + comment);
+                    }
+
+                    allVerifsPassed = false;
+                }
+            }
+            catch(Exception e)   {
+                if(_result)   {
+                    System.out.println("Exception:" + e.getMessage());
+
+                    System.out.println(" * Failed verification test.");
+                    allVerifsPassed = false;
+                }
+                else   {
+                    System.out.println(" * Passed verification test.");
+                }
+            }
+
+        }
+
+        if(allSigsPassed && allVerifsPassed)   {
+            System.out.println("All test vectors passed.");
+        }
+        else   {
+            System.out.println("Some test vectors failed.");
+        }
+
+    }
+
+}
diff --git a/java/schnorr/Pair.java b/java/schnorr/Pair.java
new file mode 100644
index 0000000..888d2e6
--- /dev/null
+++ b/java/schnorr/Pair.java
@@ -0,0 +1,34 @@
+package schnorr;
+
+// clone of org.apache.commons.lang3.tuple.Pair;
+
+public class Pair<K, V> {
+
+    private K elementLeft = null;
+    private V elementRight = null;
+
+    protected Pair() {
+    }
+
+    public static <K, V> Pair<K, V> of(K elementLeft, V elementRight) {
+        return new Pair<>(elementLeft, elementRight);
+    }
+
+    public Pair(K elementLeft, V elementRight) {
+        this.elementLeft = elementLeft;
+        this.elementRight = elementRight;
+    }
+
+    public K getLeft() {
+        return elementLeft;
+    }
+
+    public V getRight() {
+        return elementRight;
+    }
+
+    public boolean equals(Pair<K, V> p) {
+        return (this.elementLeft.equals(p.getLeft())) && (this.elementRight.equals(p.getRight()));
+    }
+
+}
diff --git a/java/schnorr/Point.java b/java/schnorr/Point.java
new file mode 100644
index 0000000..de6d81d
--- /dev/null
+++ b/java/schnorr/Point.java
@@ -0,0 +1,199 @@
+package schnorr;
+
+import java.math.BigInteger;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+public class Point  {
+
+    final static private BigInteger p = new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F", 16);
+    final static private BigInteger n = new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141", 16);
+
+    final static public Point G = new Point(
+            new BigInteger("79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798", 16),
+            new BigInteger("483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8", 16)
+    );
+
+    private static final BigInteger BI_TWO = BigInteger.valueOf(2);
+    private final Pair<BigInteger,BigInteger> pair;
+
+    public Point(BigInteger x , BigInteger y) {
+        pair = Pair.of(x, y);
+    }
+
+    public Point(byte[] b0, byte[] b1) {
+        pair = Pair.of(new BigInteger(1, b0), new BigInteger(1, b1));
+    }
+
+    public static BigInteger getp() {
+        return p;
+    }
+
+    public static BigInteger getn() {
+        return n;
+    }
+
+    public static Point getG() {
+        return G;
+    }
+
+    public BigInteger getX() {
+        return pair.getLeft();
+    }
+
+    public BigInteger getY() {
+        return pair.getRight();
+    }
+
+    public static BigInteger getX(Point P) {
+        assert !P.isInfinite();
+        return P.getX();
+    }
+
+    public static BigInteger getY(Point P) {
+        assert !P.isInfinite();
+        return P.getY();
+    }
+
+    public Pair<BigInteger,BigInteger> getPair() {
+        return pair;
+    }
+
+    public boolean isInfinite() {
+        return pair == null || pair.getLeft() == null || pair.getRight() == null;
+    }
+
+    public static boolean isInfinite(Point P) {
+        return P.isInfinite();
+    }
+
+    public Point add(Point P) {
+        return add(this, P);
+    }
+
+    public static Point add(Point P1, Point P2) {
+
+        if((P1 != null && P2 != null && P1.isInfinite() && P2.isInfinite())) {
+            return infinityPoint();
+        }
+        if(P1 == null || P1.isInfinite()) {
+            return P2;
+        }
+        if(P2 == null || P2.isInfinite()) {
+            return P1;
+        }
+        if(P1.getX().equals(P2.getX()) && !P1.getY().equals(P2.getY())) {
+            return infinityPoint();
+        }
+
+        BigInteger lam;
+        if(P1.equals(P2)) {
+            BigInteger base = P2.getY().multiply(BI_TWO);
+            lam = (BigInteger.valueOf(3L).multiply(P1.getX()).multiply(P1.getX()).multiply(base.modPow(p.subtract(BI_TWO), p))).mod(p);
+        }
+        else {
+            BigInteger base = P2.getX().subtract(P1.getX());
+            lam = ((P2.getY().subtract(P1.getY())).multiply(base.modPow(p.subtract(BI_TWO), p))).mod(p);
+        }
+
+        BigInteger x3 = (lam.multiply(lam).subtract(P1.getX()).subtract(P2.getX())).mod(p);
+        return new Point(x3, lam.multiply(P1.getX().subtract(x3)).subtract(P1.getY()).mod(p));
+    }
+
+    public Point mul(BigInteger n) {
+        return mul(this, n);
+    }
+
+    public static Point mul(Point P, BigInteger n) {
+
+        Point R = null;
+
+        for(int i = 0; i < 256; i++) {
+            if (n.shiftRight(i).and(BigInteger.ONE).compareTo(BigInteger.ZERO) > 0) {
+                R = add(R, P);
+            }
+            P = add(P, P);
+        }
+
+        return R;
+    }
+
+    public boolean hasEvenY() {
+        return hasEvenY(this);
+    }
+
+    public static boolean hasEvenY(Point P) {
+        return P.getY().mod(BI_TWO).compareTo(BigInteger.ZERO) == 0;
+    }
+
+    public static boolean isSquare(BigInteger x) {
+        return x.modPow(p.subtract(BigInteger.ONE).mod(BI_TWO), p).longValue() == 1L;
+    }
+
+    public boolean hasSquareY() {
+        return hasSquareY(this);
+    }
+
+    public static boolean hasSquareY(Point P) {
+        assert !isInfinite(P);
+        return isSquare(P.getY());
+    }
+
+    public static byte[] taggedHash(String tag, byte[] msg) throws NoSuchAlgorithmException {
+
+        MessageDigest digest = MessageDigest.getInstance("SHA-256");
+
+        byte[] tagHash = Util.sha256(tag.getBytes());
+        int len = (tagHash.length * 2) + msg.length;
+        byte[] buf = new byte[len];
+        System.arraycopy(tagHash, 0, buf, 0, tagHash.length);
+        System.arraycopy(tagHash, 0, buf, tagHash.length, tagHash.length);
+        System.arraycopy(msg, 0, buf, tagHash.length * 2, msg.length);
+
+        return Util.sha256(buf);
+    }
+
+    public static byte[] genPubKey(byte[] secKey) throws Exception {
+        BigInteger x = Util.bigIntFromBytes(secKey);
+        if(!(BigInteger.ONE.compareTo(x) <= 0 && x.compareTo(getn().subtract(BigInteger.ONE)) <= 0)) {
+            throw new Exception("The secret key must be an integer in the range 1..n-1.");
+        }
+        Point ret = Point.mul(G, x);
+        return bytesFromPoint(ret);
+    }
+
+    public byte[] toBytes() {
+        return bytesFromPoint(this);
+    }
+
+    public static byte[] bytesFromPoint(Point P) {
+        return Util.bytesFromBigInteger(P.getX());
+    }
+
+    // previously 'pointFromBytes()'
+    public static Point liftX(byte[] b) {
+
+        BigInteger x = Util.bigIntFromBytes(b);
+        if(x.compareTo(p) >= 0) {
+            return null;
+        }
+        BigInteger y_sq = x.modPow(BigInteger.valueOf(3L), p).add(BigInteger.valueOf(7L)).mod(p);
+        BigInteger y = y_sq.modPow(p.add(BigInteger.ONE).divide(BigInteger.valueOf(4L)), p);
+
+        if(y.modPow(BI_TWO, p).compareTo(y_sq) != 0) {
+            return null;
+        }
+        else {
+            return new Point(x, y.and(BigInteger.ONE).compareTo(BigInteger.ZERO) == 0 ? y : p.subtract(y));
+        }
+    }
+
+    public static Point infinityPoint() {
+        return new Point(null, (BigInteger) null);
+    }
+
+    public boolean equals(Point P) {
+        return getPair().equals(P.getPair());
+    }
+
+}
diff --git a/java/schnorr/Schnorr.java b/java/schnorr/Schnorr.java
new file mode 100644
index 0000000..4491a81
--- /dev/null
+++ b/java/schnorr/Schnorr.java
@@ -0,0 +1,95 @@
+package schnorr;
+
+import java.math.BigInteger;
+import java.util.Arrays;
+
+public class Schnorr    {
+
+    public static byte[] sign(byte[] msg, byte[] secKey, byte[] auxRand) throws Exception    {
+        if(msg.length != 32)    {
+            throw new Exception("The message must be a 32-byte array.");
+        }
+        BigInteger secKey0 = Util.bigIntFromBytes(secKey);
+
+        if(!(BigInteger.ONE.compareTo(secKey0) <= 0 && secKey0.compareTo(Point.getn().subtract(BigInteger.ONE)) <= 0)) {
+            throw new Exception("The secret key must be an integer in the range 1..n-1.");
+        }
+        Point P = Point.mul(Point.getG(), secKey0);
+        if(!P.hasEvenY())    {
+            secKey0 = Point.getn().subtract(secKey0);
+        }
+        int len = Util.bytesFromBigInteger(secKey0).length + P.toBytes().length + msg.length;
+        byte[] buf = new byte[len];
+        byte[] t = Util.xor(Util.bytesFromBigInteger(secKey0), Point.taggedHash("BIP0340/aux", auxRand));
+        System.arraycopy(t, 0, buf, 0, t.length);
+        System.arraycopy(P.toBytes(), 0, buf, t.length, P.toBytes().length);
+        System.arraycopy(msg, 0, buf, t.length + P.toBytes().length, msg.length);
+        BigInteger k0 = Util.bigIntFromBytes(Point.taggedHash("BIP0340/nonce", buf)).mod(Point.getn());
+        if(k0.compareTo(BigInteger.ZERO) == 0)    {
+            throw new Exception("Failure. This happens only with negligible probability.");
+        }
+        Point R = Point.mul(Point.getG(), k0);
+        BigInteger k;
+        if(!R.hasEvenY())    {
+            k = Point.getn().subtract(k0);
+        }
+        else    {
+            k = k0;
+        }
+        len = R.toBytes().length + P.toBytes().length + msg.length;
+        buf = new byte[len];
+        System.arraycopy(R.toBytes(), 0, buf, 0, R.toBytes().length);
+        System.arraycopy(P.toBytes(), 0, buf, R.toBytes().length, P.toBytes().length);
+        System.arraycopy(msg, 0, buf, R.toBytes().length + P.toBytes().length, msg.length);
+        BigInteger e = Util.bigIntFromBytes(Point.taggedHash("BIP0340/challenge", buf)).mod(Point.getn());
+        BigInteger kes = k.add(e.multiply(secKey0)).mod(Point.getn());
+        len = R.toBytes().length + Util.bytesFromBigInteger(kes).length;
+        byte[] sig = new byte[len];
+        System.arraycopy(R.toBytes(), 0, sig, 0, R.toBytes().length);
+        System.arraycopy(Util.bytesFromBigInteger(kes), 0, sig, R.toBytes().length, Util.bytesFromBigInteger(kes).length);
+        if(!verify(msg, P.toBytes(), sig))    {
+            throw new Exception("The signature does not pass verification.");
+        }
+        return sig;
+    }
+
+    public static boolean verify(byte[] msg, byte[] pubkey, byte[] sig) throws Exception    {
+        if(msg.length != 32)    {
+            throw new Exception("The message must be a 32-byte array.");
+        }
+        if(pubkey.length != 32)    {
+            throw new Exception("The public key must be a 32-byte array.");
+        }
+        if(sig.length != 64)    {
+            throw new Exception("The signature must be a 64-byte array.");
+        }
+
+        Point P = Point.liftX(pubkey);
+        if(P == null)    {
+            return false;
+        }
+        BigInteger r = Util.bigIntFromBytes(Arrays.copyOfRange(sig,0, 32));
+        BigInteger s = Util.bigIntFromBytes(Arrays.copyOfRange(sig,32, 64));
+        if(r.compareTo(Point.getp()) >= 0 || s.compareTo(Point.getn()) >= 0)    {
+            return false;
+        }
+        int len = 32 + pubkey.length + msg.length;
+        byte[] buf = new byte[len];
+        System.arraycopy(sig, 0, buf, 0, 32);
+        System.arraycopy(pubkey, 0, buf, 32, pubkey.length);
+        System.arraycopy(msg, 0, buf, 32 + pubkey.length, msg.length);
+        BigInteger e = Util.bigIntFromBytes(Point.taggedHash("BIP0340/challenge", buf)).mod(Point.getn());
+        Point R = Point.add(Point.mul(Point.getG(), s), Point.mul(P, Point.getn().subtract(e)));
+      return R != null && R.hasEvenY() && R.getX().compareTo(r) == 0;
+    }
+
+    public static byte[] genPubKey(byte[] secKey) throws Exception {
+        BigInteger x = Util.bigIntFromBytes(secKey);
+        if(!(BigInteger.ONE.compareTo(x) <= 0 && x.compareTo(Point.getn().subtract(BigInteger.ONE)) <= 0)) {
+            throw new Exception("The secret key must be an integer in the range 1..n-1.");
+        }
+        Point ret = Point.mul(Point.G, x);
+        return Point.bytesFromPoint(ret);
+    }
+
+}
diff --git a/java/schnorr/Util.java b/java/schnorr/Util.java
new file mode 100644
index 0000000..de05463
--- /dev/null
+++ b/java/schnorr/Util.java
@@ -0,0 +1,79 @@
+package schnorr;
+
+import java.math.BigInteger;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Arrays;
+
+public class Util  {
+
+    private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
+
+    public static String bytesToHex(byte[] b) {
+        char[] hexChars = new char[b.length * 2];
+        for (int j = 0; j < b.length; j++) {
+            int v = b[j] & 0xFF;
+            hexChars[j * 2] = HEX_ARRAY[v >>> 4];
+            hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
+        }
+        return new String(hexChars);
+    }
+
+    public static byte[] hexToBytes(String s) {
+        int len = s.length();
+        byte[] buf = new byte[len / 2];
+        for (int i = 0; i < len; i += 2) {
+            buf[i / 2] = (byte)((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i+1), 16));
+        }
+        return buf;
+    }
+
+    public static byte[] bytesFromInt(int n) {
+        return ByteBuffer.allocate(4).order(ByteOrder.BIG_ENDIAN).putInt(n).array();
+    }
+
+    public static byte[] bytesFromBigInteger(BigInteger n) {
+
+        byte[] b = n.toByteArray();
+
+        if(b.length == 32) {
+            return b;
+        }
+        else if(b.length > 32) {
+            return Arrays.copyOfRange(b, b.length - 32, b.length);
+        }
+        else {
+            byte[] buf = new byte[32];
+            System.arraycopy(b, 0, buf, buf.length - b.length, b.length);
+            return buf;
+        }
+    }
+
+    public static BigInteger bigIntFromBytes(byte[] b) {
+        return new BigInteger(1, b);
+    }
+
+    public static byte[] sha256(byte[] b) throws NoSuchAlgorithmException {
+        MessageDigest digest = MessageDigest.getInstance("SHA-256");
+        return digest.digest(b);
+    }
+
+    public static byte[] xor(byte[] b0, byte[] b1)   {
+
+        if(b0.length != b1.length)   {
+            return  null;
+        }
+
+        byte[] ret = new byte[b0.length];
+        int i = 0;
+        for (byte b : b0)   {
+            ret[i] = (byte)(b ^ b1[i]);
+            i++;
+        }
+
+        return ret;
+    }
+
+}