package org.ethereum.crypto;
/**
* Copyright 2011 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import static org.ethereum.util.ByteUtil.bigIntegerToBytes;
import java.io.Serializable;
import java.math.BigInteger;
import java.nio.charset.Charset;
import java.security.SecureRandom;
import java.security.SignatureException;
import java.util.Arrays;
import javax.annotation.Nullable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.spongycastle.asn1.sec.SECNamedCurves;
import org.spongycastle.asn1.x9.X9ECParameters;
import org.spongycastle.asn1.x9.X9IntegerConverter;
import org.spongycastle.crypto.AsymmetricCipherKeyPair;
import org.spongycastle.crypto.digests.SHA256Digest;
import org.spongycastle.crypto.generators.ECKeyPairGenerator;
import org.spongycastle.crypto.params.ECDomainParameters;
import org.spongycastle.crypto.params.ECKeyGenerationParameters;
import org.spongycastle.crypto.params.ECPrivateKeyParameters;
import org.spongycastle.crypto.params.ECPublicKeyParameters;
import org.spongycastle.crypto.signers.ECDSASigner;
import org.spongycastle.crypto.signers.HMacDSAKCalculator;
import org.spongycastle.math.ec.ECAlgorithms;
import org.spongycastle.math.ec.ECCurve;
import org.spongycastle.math.ec.ECPoint;
import org.spongycastle.util.encoders.Base64;
import org.spongycastle.util.encoders.Hex;
/**
* <p>Represents an elliptic curve public and (optionally) private key, usable for digital signatures but not encryption.
* Creating a new ECKey with the empty constructor will generate a new random keypair. Other static methods can be used
* when you already have the public or private parts. If you create a key with only the public part, you can check
* signatures but not create them.</p>
*
* <p>The ECDSA algorithm supports <i>key recovery</i> in which a signature plus a couple of discriminator bits can
* be reversed to find the public key used to calculate it. This can be convenient when you have a message and a
* signature and want to find out who signed it, rather than requiring the user to provide the expected identity.</p>
*
* <p>A key can be <i>compressed</i> or <i>uncompressed</i>. This refers to whether the public key is represented
* when encoded into bytes as an (x, y) coordinate on the elliptic curve, or whether it's represented as just an X
* co-ordinate and an extra byte that carries a sign bit. With the latter form the Y coordinate can be calculated
* dynamically, however, <b>because the binary serialization is different the address of a key changes if its
* compression status is changed</b>. If you deviate from the defaults it's important to understand this: money sent
* to a compressed version of the key will have a different address to the same key in uncompressed form. Whether
* a public key is compressed or not is recorded in the SEC binary serialisation format, and preserved in a flag in
* this class so round-tripping preserves state. Unless you're working with old software or doing unusual things, you
* can usually ignore the compressed/uncompressed distinction.</p>
*
* This code is borrowed from the bitcoinj project and altered to fit Ethereum.<br>
* See <a href="https://github.com/bitcoinj/bitcoinj/blob/master/core/src/main/java/com/google/bitcoin/core/ECKey.java">bitcoinj on GitHub</a>
*/
public class ECKey implements Serializable {
private static final Logger logger = LoggerFactory.getLogger(ECKey.class);
/** The parameters of the secp256k1 curve that Ethereum uses. */
public static final ECDomainParameters CURVE;
/**
* Equal to CURVE.getN().shiftRight(1), used for canonicalising the S value of a signature. If you aren't
* sure what this is about, you can ignore it.
*/
public static final BigInteger HALF_CURVE_ORDER;
private static final SecureRandom secureRandom;
private static final long serialVersionUID = -728224901792295832L;
static {
// All clients must agree on the curve to use by agreement. Ethereum uses secp256k1.
X9ECParameters params = SECNamedCurves.getByName("secp256k1");
CURVE = new ECDomainParameters(params.getCurve(), params.getG(), params.getN(), params.getH());
HALF_CURVE_ORDER = params.getN().shiftRight(1);
secureRandom = new SecureRandom();
}
// The two parts of the key. If "priv" is set, "pub" can always be calculated. If "pub" is set but not "priv", we
// can only verify signatures not make them.
// TODO: Redesign this class to use consistent internals and more efficient serialization.
private BigInteger priv;
protected final ECPoint pub;
// Transient because it's calculated on demand.
transient private byte[] pubKeyHash;
/**
* Generates an entirely new keypair. Point compression is used so the resulting public key will be 33 bytes
* (32 for the co-ordinate and 1 byte to represent the y bit).
*/
public ECKey() {
this(secureRandom);
}
/**
* Generates an entirely new keypair with the given {@link SecureRandom} object. Point compression is used so the
* resulting public key will be 33 bytes (32 for the co-ordinate and 1 byte to represent the y bit).
*/
public ECKey(SecureRandom secureRandom) {
ECKeyPairGenerator generator = new ECKeyPairGenerator();
ECKeyGenerationParameters keygenParams = new ECKeyGenerationParameters(CURVE, secureRandom);
generator.init(keygenParams);
AsymmetricCipherKeyPair keypair = generator.generateKeyPair();
ECPrivateKeyParameters privParams = (ECPrivateKeyParameters) keypair.getPrivate();
ECPublicKeyParameters pubParams = (ECPublicKeyParameters) keypair.getPublic();
priv = privParams.getD();
pub = CURVE.getCurve().decodePoint(pubParams.getQ().getEncoded(true));
}
public ECKey(@Nullable BigInteger priv, ECPoint pub) {
this.priv = priv;
if(pub == null)
throw new IllegalArgumentException("Public key may not be null");
this.pub = pub;
}
/**
* Utility for compressing an elliptic curve point. Returns the same point if it's already compressed.
* See the ECKey class docs for a discussion of point compression.
*/
public static ECPoint compressPoint(ECPoint uncompressed) {
return CURVE.getCurve().decodePoint(uncompressed.getEncoded(true));
}
/**
* Utility for decompressing an elliptic curve point. Returns the same point if it's already compressed.
* See the ECKey class docs for a discussion of point compression.
*/
public static ECPoint decompressPoint(ECPoint compressed) {
return CURVE.getCurve().decodePoint(compressed.getEncoded(false));
}
/**
* Creates an ECKey given the private key only. The public key is calculated from it (this is slow). Note that
* the resulting public key is compressed.
*/
public static ECKey fromPrivate(BigInteger privKey) {
return new ECKey(privKey, compressPoint(CURVE.getG().multiply(privKey)));
}
/**
* Creates an ECKey given the private key only. The public key is calculated from it (this is slow). The resulting
* public key is compressed.
*/
public static ECKey fromPrivate(byte[] privKeyBytes) {
return fromPrivate(new BigInteger(1, privKeyBytes));
}
/**
* Creates an ECKey that simply trusts the caller to ensure that point is really the result of multiplying the
* generator point by the private key. This is used to speed things up when you know you have the right values
* already. The compression state of pub will be preserved.
*/
public static ECKey fromPrivateAndPrecalculatedPublic(BigInteger priv, ECPoint pub) {
return new ECKey(priv, pub);
}
/**
* Creates an ECKey that simply trusts the caller to ensure that point is really the result of multiplying the
* generator point by the private key. This is used to speed things up when you know you have the right values
* already. The compression state of the point will be preserved.
*/
public static ECKey fromPrivateAndPrecalculatedPublic(byte[] priv, byte[] pub) {
check(priv != null, "Private key must not be null");
check(pub != null, "Public key must not be null");
return new ECKey(new BigInteger(1, priv), CURVE.getCurve().decodePoint(pub));
}
/**
* Creates an ECKey that cannot be used for signing, only verifying signatures, from the given point. The
* compression state of pub will be preserved.
*/
public static ECKey fromPublicOnly(ECPoint pub) {
return new ECKey(null, pub);
}
/**
* Creates an ECKey that cannot be used for signing, only verifying signatures, from the given encoded point.
* The compression state of pub will be preserved.
*/
public static ECKey fromPublicOnly(byte[] pub) {
return new ECKey(null, CURVE.getCurve().decodePoint(pub));
}
/**
* Returns a copy of this key, but with the public point represented in uncompressed form. Normally you would
* never need this: it's for specialised scenarios or when backwards compatibility in encoded form is necessary.
*/
public ECKey decompress() {
if (!pub.isCompressed())
return this;
else
return new ECKey(priv, decompressPoint(pub));
}
/**
* Returns true if this key doesn't have access to private key bytes. This may be because it was never
* given any private key bytes to begin with (a watching key).
*/
public boolean isPubKeyOnly() {
return priv == null;
}
/**
* Returns true if this key has access to private key bytes. Does the opposite of
* {@link #isPubKeyOnly()}.
*/
public boolean hasPrivKey() {
return priv != null;
}
/**
* Returns public key bytes from the given private key. To convert a byte array into a BigInteger, use <tt>
* new BigInteger(1, bytes);</tt>
*/
public static byte[] publicKeyFromPrivate(BigInteger privKey, boolean compressed) {
ECPoint point = CURVE.getG().multiply(privKey);
return point.getEncoded(compressed);
}
/** Gets the hash160 form of the public key (as seen in addresses). */
public byte[] getAddress() {
if (pubKeyHash == null) {
byte[] pubBytes = this.pub.getEncoded(false);
pubKeyHash = HashUtil.sha3omit12(Arrays.copyOfRange(pubBytes, 1, pubBytes.length));
}
return pubKeyHash;
}
/**
* Gets the raw public key value. This appears in transaction scriptSigs. Note that this is <b>not</b> the same
* as the pubKeyHash/address.
*/
public byte[] getPubKey() {
return pub.getEncoded();
}
/** Gets the public key in the form of an elliptic curve point object from Bouncy Castle. */
public ECPoint getPubKeyPoint() {
return pub;
}
/**
* Gets the private key in the form of an integer field element. The public key is derived by performing EC
* point addition this number of times (i.e. point multiplying).
*
* @throws java.lang.IllegalStateException if the private key bytes are not available.
*/
public BigInteger getPrivKey() {
if (priv == null)
throw new MissingPrivateKeyException();
return priv;
}
/**
* Returns whether this key is using the compressed form or not. Compressed pubkeys are only 33 bytes, not 64.
*/
public boolean isCompressed() {
return pub.isCompressed();
}
public String toString() {
StringBuilder b = new StringBuilder();
b.append("pub:").append(Hex.toHexString(pub.getEncoded(false)));
return b.toString();
}
/**
* Produce a string rendering of the ECKey INCLUDING the private key.
* Unless you absolutely need the private key it is better for security reasons to just use toString().
*/
public String toStringWithPrivate() {
StringBuilder b = new StringBuilder();
b.append(toString());
if (priv != null) {
b.append(" priv:").append(Hex.toHexString(priv.toByteArray()));
}
return b.toString();
}
/**
* Groups the two components that make up a signature, and provides a way to encode to Base64 form, which is
* how ECDSA signatures are represented when embedded in other data structures in the Ethereum protocol. The raw
* components can be useful for doing further EC maths on them.
*/
public static class ECDSASignature {
/** The two components of the signature. */
public final BigInteger r, s;
public byte v;
/**
* Constructs a signature with the given components. Does NOT automatically canonicalise the signature.
*/
public ECDSASignature(BigInteger r, BigInteger s) {
this.r = r;
this.s = s;
}
private static ECDSASignature fromComponents(byte[] r, byte[] s) {
return new ECDSASignature(new BigInteger(1, r), new BigInteger(1, s));
}
public static ECDSASignature fromComponents(byte[] r, byte[] s, byte v) {
ECDSASignature signature = fromComponents(r, s);
signature.v = v;
return signature;
}
/**
* Will automatically adjust the S component to be less than or equal to half the curve order, if necessary.
* This is required because for every signature (r,s) the signature (r, -s (mod N)) is a valid signature of
* the same message. However, we dislike the ability to modify the bits of a Ethereum transaction after it's
* been signed, as that violates various assumed invariants. Thus in future only one of those forms will be
* considered legal and the other will be banned.
*/
public ECDSASignature toCanonicalised() {
if (s.compareTo(HALF_CURVE_ORDER) > 0) {
// The order of the curve is the number of valid points that exist on that curve. If S is in the upper
// half of the number of valid points, then bring it back to the lower half. Otherwise, imagine that
// N = 10
// s = 8, so (-8 % 10 == 2) thus both (r, 8) and (r, 2) are valid solutions.
// 10 - 8 == 2, giving us always the latter solution, which is canonical.
return new ECDSASignature(r, CURVE.getN().subtract(s));
} else {
return this;
}
}
public String toBase64() {
byte[] sigData = new byte[65]; // 1 header + 32 bytes for R + 32 bytes for S
sigData[0] = v;
System.arraycopy(bigIntegerToBytes(this.r, 32), 0, sigData, 1, 32);
System.arraycopy(bigIntegerToBytes(this.s, 32), 0, sigData, 33, 32);
return new String(Base64.encode(sigData), Charset.forName("UTF-8"));
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
ECDSASignature signature = (ECDSASignature) o;
if (!r.equals(signature.r)) return false;
if (!s.equals(signature.s)) return false;
return true;
}
@Override
public int hashCode() {
int result = r.hashCode();
result = 31 * result + s.hashCode();
return result;
}
}
/**
* Signs the given hash and returns the R and S components as BigIntegers
* and put them in ECDSASignature
*
* @param input to sign
* @return ECDSASignature signature that contains the R and S components
*/
public ECDSASignature doSign(byte[] input) {
// No decryption of private key required.
if (priv == null)
throw new MissingPrivateKeyException();
check(priv != null, "Private key must not be null");
ECDSASigner signer = new ECDSASigner(new HMacDSAKCalculator(new SHA256Digest()));
ECPrivateKeyParameters privKey = new ECPrivateKeyParameters(priv, CURVE);
signer.init(true, privKey);
BigInteger[] components = signer.generateSignature(input);
return new ECDSASignature(components[0], components[1]).toCanonicalised();
}
/**
* Takes the sha3 hash (32 bytes) of data and returns the ECDSA signature
*
* @throws IllegalStateException if this ECKey does not have the private part.
*/
public ECDSASignature sign(byte[] messageHash) {
if (priv == null)
throw new MissingPrivateKeyException();
ECDSASignature sig = doSign(messageHash);
// Now we have to work backwards to figure out the recId needed to recover the signature.
int recId = -1;
for (int i = 0; i < 4; i++) {
ECKey k = ECKey.recoverFromSignature(i, sig, messageHash, isCompressed());
if (k != null && k.pub.equals(pub)) {
recId = i;
break;
}
}
if (recId == -1)
throw new RuntimeException("Could not construct a recoverable key. This should never happen.");
sig.v = (byte) (recId + 27 + (isCompressed() ? 4 : 0));
return sig;
}
/**
* Given a piece of text and a message signature encoded in base64, returns an ECKey
* containing the public key that was used to sign it. This can then be compared to the expected public key to
* determine if the signature was correct.
*
* @param messageHash a piece of human readable text that was signed
* @param signatureBase64 The Ethereum-format message signature in base64
* @throws SignatureException If the public key could not be recovered or if there was a signature format error.
*/
public static ECKey signatureToKey(byte[] messageHash, String signatureBase64) throws SignatureException {
byte[] signatureEncoded;
try {
signatureEncoded = Base64.decode(signatureBase64);
} catch (RuntimeException e) {
// This is what you get back from Bouncy Castle if base64 doesn't decode :(
throw new SignatureException("Could not decode base64", e);
}
// Parse the signature bytes into r/s and the selector value.
if (signatureEncoded.length < 65)
throw new SignatureException("Signature truncated, expected 65 bytes and got " + signatureEncoded.length);
int header = signatureEncoded[0] & 0xFF;
// The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
// 0x1D = second key with even y, 0x1E = second key with odd y
if (header < 27 || header > 34)
throw new SignatureException("Header byte out of range: " + header);
BigInteger r = new BigInteger(1, Arrays.copyOfRange(signatureEncoded, 1, 33));
BigInteger s = new BigInteger(1, Arrays.copyOfRange(signatureEncoded, 33, 65));
ECDSASignature sig = new ECDSASignature(r, s);
boolean compressed = false;
if (header >= 31) {
compressed = true;
header -= 4;
}
int recId = header - 27;
ECKey key = ECKey.recoverFromSignature(recId, sig, messageHash, compressed);
if (key == null)
throw new SignatureException("Could not recover public key from signature");
return key;
}
/**
* <p>Verifies the given ECDSA signature against the message bytes using the public key bytes.</p>
*
* <p>When using native ECDSA verification, data must be 32 bytes, and no element may be
* larger than 520 bytes.</p>
*
* @param data Hash of the data to verify.
* @param signature signature.
* @param pub The public key bytes to use.
*/
public static boolean verify(byte[] data, ECDSASignature signature, byte[] pub) {
ECDSASigner signer = new ECDSASigner();
ECPublicKeyParameters params = new ECPublicKeyParameters(CURVE.getCurve().decodePoint(pub), CURVE);
signer.init(false, params);
try {
return signer.verifySignature(data, signature.r, signature.s);
} catch (NullPointerException npe) {
// Bouncy Castle contains a bug that can cause NPEs given specially crafted signatures.
// Those signatures are inherently invalid/attack sigs so we just fail them here rather than crash the thread.
logger.error("Caught NPE inside bouncy castle", npe);
return false;
}
}
/**
* Verifies the given ASN.1 encoded ECDSA signature against a hash using the public key.
*
* @param data Hash of the data to verify.
* @param signature signature.
* @param pub The public key bytes to use.
*/
public static boolean verify(byte[] data, byte[] signature, byte[] pub) {
return verify(data, signature, pub);
}
/**
* Verifies the given ASN.1 encoded ECDSA signature against a hash using the public key.
*
* @param data Hash of the data to verify.
* @param signature signature.
*/
public boolean verify(byte[] data, byte[] signature) {
return ECKey.verify(data, signature, getPubKey());
}
/**
* Verifies the given R/S pair (signature) against a hash using the public key.
*/
public boolean verify(byte[] sigHash, ECDSASignature signature) {
return ECKey.verify(sigHash, signature, getPubKey());
}
/**
* Returns true if this pubkey is canonical, i.e. the correct length taking into account compression.
*/
public boolean isPubKeyCanonical() {
return isPubKeyCanonical(pub.getEncoded());
}
/**
* Returns true if the given pubkey is canonical, i.e. the correct length taking into account compression.
*/
public static boolean isPubKeyCanonical(byte[] pubkey) {
if (pubkey[0] == 0x04) {
// Uncompressed pubkey
if (pubkey.length != 65)
return false;
} else if (pubkey[0] == 0x02 || pubkey[0] == 0x03) {
// Compressed pubkey
if (pubkey.length != 33)
return false;
} else
return false;
return true;
}
/**
* <p>Given the components of a signature and a selector value, recover and return the public key
* that generated the signature according to the algorithm in SEC1v2 section 4.1.6.</p>
*
* <p>The recId is an index from 0 to 3 which indicates which of the 4 possible keys is the correct one. Because
* the key recovery operation yields multiple potential keys, the correct key must either be stored alongside the
* signature, or you must be willing to try each recId in turn until you find one that outputs the key you are
* expecting.</p>
*
* <p>If this method returns null it means recovery was not possible and recId should be iterated.</p>
*
* <p>Given the above two points, a correct usage of this method is inside a for loop from 0 to 3, and if the
* output is null OR a key that is not the one you expect, you try again with the next recId.</p>
*
* @param recId Which possible key to recover.
* @param sig the R and S components of the signature, wrapped.
* @param messageHash Hash of the data that was signed.
* @param compressed Whether or not the original pubkey was compressed.
* @return An ECKey containing only the public part, or null if recovery wasn't possible.
*/
@Nullable
public static ECKey recoverFromSignature(int recId, ECDSASignature sig, byte[] messageHash, boolean compressed) {
check(recId >= 0, "recId must be positive");
check(sig.r.signum() >= 0, "r must be positive");
check(sig.s.signum() >= 0, "s must be positive");
check(messageHash != null, "messageHash must not be null");
// 1.0 For j from 0 to h (h == recId here and the loop is outside this function)
// 1.1 Let x = r + jn
BigInteger n = CURVE.getN(); // Curve order.
BigInteger i = BigInteger.valueOf((long) recId / 2);
BigInteger x = sig.r.add(i.multiply(n));
// 1.2. Convert the integer x to an octet string X of length mlen using the conversion routine
// specified in Section 2.3.7, where mlen = ⌈(log2 p)/8⌉ or mlen = ⌈m/8⌉.
// 1.3. Convert the octet string (16 set binary digits)||X to an elliptic curve point R using the
// conversion routine specified in Section 2.3.4. If this conversion routine outputs “invalid”, then
// do another iteration of Step 1.
//
// More concisely, what these points mean is to use X as a compressed public key.
ECCurve.Fp curve = (ECCurve.Fp) CURVE.getCurve();
BigInteger prime = curve.getQ(); // Bouncy Castle is not consistent about the letter it uses for the prime.
if (x.compareTo(prime) >= 0) {
// Cannot have point co-ordinates larger than this as everything takes place modulo Q.
return null;
}
// Compressed keys require you to know an extra bit of data about the y-coord as there are two possibilities.
// So it's encoded in the recId.
ECPoint R = decompressKey(x, (recId & 1) == 1);
// 1.4. If nR != point at infinity, then do another iteration of Step 1 (callers responsibility).
if (!R.multiply(n).isInfinity())
return null;
// 1.5. Compute e from M using Steps 2 and 3 of ECDSA signature verification.
BigInteger e = new BigInteger(1, messageHash);
// 1.6. For k from 1 to 2 do the following. (loop is outside this function via iterating recId)
// 1.6.1. Compute a candidate public key as:
// Q = mi(r) * (sR - eG)
//
// Where mi(x) is the modular multiplicative inverse. We transform this into the following:
// Q = (mi(r) * s ** R) + (mi(r) * -e ** G)
// Where -e is the modular additive inverse of e, that is z such that z + e = 0 (mod n). In the above equation
// ** is point multiplication and + is point addition (the EC group operator).
//
// We can find the additive inverse by subtracting e from zero then taking the mod. For example the additive
// inverse of 3 modulo 11 is 8 because 3 + 8 mod 11 = 0, and -3 mod 11 = 8.
BigInteger eInv = BigInteger.ZERO.subtract(e).mod(n);
BigInteger rInv = sig.r.modInverse(n);
BigInteger srInv = rInv.multiply(sig.s).mod(n);
BigInteger eInvrInv = rInv.multiply(eInv).mod(n);
ECPoint.Fp q = (ECPoint.Fp) ECAlgorithms.sumOfTwoMultiplies(CURVE.getG(), eInvrInv, R, srInv);
return ECKey.fromPublicOnly(q.getEncoded(compressed));
}
/** Decompress a compressed public key (x co-ord and low-bit of y-coord). */
private static ECPoint decompressKey(BigInteger xBN, boolean yBit) {
X9IntegerConverter x9 = new X9IntegerConverter();
byte[] compEnc = x9.integerToBytes(xBN, 1 + x9.getByteLength(CURVE.getCurve()));
compEnc[0] = (byte)(yBit ? 0x03 : 0x02);
return CURVE.getCurve().decodePoint(compEnc);
}
/**
* Returns a 32 byte array containing the private key, or null if the key is encrypted or public only
*/
@Nullable
public byte[] getPrivKeyBytes() {
return bigIntegerToBytes(priv, 32);
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || !(o instanceof ECKey)) return false;
ECKey ecKey = (ECKey) o;
if (priv != null && !priv.equals(ecKey.priv)) return false;
if (pub != null && !pub.equals(ecKey.pub)) return false;
return true;
}
@Override
public int hashCode() {
// Public keys are random already so we can just use a part of them as the hashcode. Read from the start to
// avoid picking up the type code (compressed vs uncompressed) which is tacked on the end.
byte[] bits = getPubKey();
return (bits[0] & 0xFF) | ((bits[1] & 0xFF) << 8) | ((bits[2] & 0xFF) << 16) | ((bits[3] & 0xFF) << 24);
}
@SuppressWarnings("serial")
public static class MissingPrivateKeyException extends RuntimeException {
}
private static void check(boolean test, String message) {
if(!test) throw new IllegalArgumentException(message);
}
}