add support for dumped private keys

src/main/java/com/sparrowwallet/drongo/Network.java

@@ -1,14 +1,14 @@
 package com.sparrowwallet.drongo;
 
 public enum Network {
-    MAINNET("mainnet", 0, "1", 5, "3", "bc", ExtendedKey.Header.xprv, ExtendedKey.Header.xpub, 8332),
-    TESTNET("testnet", 111, "mn", 196, "2", "tb", ExtendedKey.Header.tprv, ExtendedKey.Header.tpub, 18332),
-    REGTEST("regtest", 111, "mn", 196, "2", "bcrt", ExtendedKey.Header.tprv, ExtendedKey.Header.tpub, 18443),
-    SIGNET("signet", 111, "mn", 196, "2", "tb", ExtendedKey.Header.tprv, ExtendedKey.Header.tpub, 38332);
+    MAINNET("mainnet", 0, "1", 5, "3", "bc", ExtendedKey.Header.xprv, ExtendedKey.Header.xpub, 128, 8332),
+    TESTNET("testnet", 111, "mn", 196, "2", "tb", ExtendedKey.Header.tprv, ExtendedKey.Header.tpub, 239, 18332),
+    REGTEST("regtest", 111, "mn", 196, "2", "bcrt", ExtendedKey.Header.tprv, ExtendedKey.Header.tpub, 239, 18443),
+    SIGNET("signet", 111, "mn", 196, "2", "tb", ExtendedKey.Header.tprv, ExtendedKey.Header.tpub, 239, 38332);
 
     public static final String BLOCK_HEIGHT_PROPERTY = "com.sparrowwallet.blockHeight";
 
-    Network(String name, int p2pkhAddressHeader, String p2pkhAddressPrefix, int p2shAddressHeader, String p2shAddressPrefix, String bech32AddressHrp, ExtendedKey.Header xprvHeader, ExtendedKey.Header xpubHeader, int defaultPort) {
+    Network(String name, int p2pkhAddressHeader, String p2pkhAddressPrefix, int p2shAddressHeader, String p2shAddressPrefix, String bech32AddressHrp, ExtendedKey.Header xprvHeader, ExtendedKey.Header xpubHeader, int dumpedPrivateKeyHeader, int defaultPort) {
         this.name = name;
         this.p2pkhAddressHeader = p2pkhAddressHeader;
         this.p2pkhAddressPrefix = p2pkhAddressPrefix;
@@ -17,6 +17,7 @@ public enum Network {
         this.bech32AddressHrp = bech32AddressHrp;
         this.xprvHeader = xprvHeader;
         this.xpubHeader = xpubHeader;
+        this.dumpedPrivateKeyHeader = dumpedPrivateKeyHeader;
         this.defaultPort = defaultPort;
     }
 
@@ -28,6 +29,7 @@ public enum Network {
     private final String bech32AddressHrp;
     private final ExtendedKey.Header xprvHeader;
     private final ExtendedKey.Header xpubHeader;
+    private final int dumpedPrivateKeyHeader;
     private final int defaultPort;
 
     private static Network currentNetwork;
@@ -56,6 +58,10 @@ public enum Network {
         return xpubHeader;
     }
 
+    public int getDumpedPrivateKeyHeader() {
+        return dumpedPrivateKeyHeader;
+    }
+
     public int getDefaultPort() {
         return defaultPort;
     }

src/main/java/com/sparrowwallet/drongo/crypto/DumpedPrivateKey.java

@@ -0,0 +1,88 @@
+package com.sparrowwallet.drongo.crypto;
+
+
+import com.sparrowwallet.drongo.Network;
+
+import java.util.Arrays;
+import java.util.Objects;
+
+/**
+ * Parses and generates private keys in the form used by the Bitcoin "dumpprivkey" command. This is the private key
+ * bytes with a header byte and 4 checksum bytes at the end. If there are 33 private key bytes instead of 32, then
+ * the last byte is a discriminator value for the compressed pubkey.
+ */
+public class DumpedPrivateKey extends VersionedChecksummedBytes {
+    private final boolean compressed;
+
+    /**
+     * Construct a private key from its Base58 representation.
+     * @param base58
+     *            The textual form of the private key.
+     */
+    public static DumpedPrivateKey fromBase58(String base58) {
+        return new DumpedPrivateKey(base58);
+    }
+
+    // Used by ECKey.getPrivateKeyEncoded()
+    DumpedPrivateKey(byte[] keyBytes, boolean compressed) {
+        super(Network.get().getDumpedPrivateKeyHeader(), encode(keyBytes, compressed));
+        this.compressed = compressed;
+    }
+
+    private static byte[] encode(byte[] keyBytes, boolean compressed) {
+        if(keyBytes.length != 32) {
+            throw new IllegalArgumentException("Private keys must be 32 bytes");
+        }
+
+        if (!compressed) {
+            return keyBytes;
+        } else {
+            // Keys that have compressed public components have an extra 1 byte on the end in dumped form.
+            byte[] bytes = new byte[33];
+            System.arraycopy(keyBytes, 0, bytes, 0, 32);
+            bytes[32] = 1;
+            return bytes;
+        }
+    }
+
+    private DumpedPrivateKey(String encoded) {
+        super(encoded);
+        if(version != Network.get().getDumpedPrivateKeyHeader())
+            throw new IllegalArgumentException("Invalid version " + version + " for network " + Network.get());
+        if(bytes.length == 33 && bytes[32] == 1) {
+            compressed = true;
+            bytes = Arrays.copyOf(bytes, 32);  // Chop off the additional marker byte.
+        } else if(bytes.length == 32) {
+            compressed = false;
+        } else {
+            throw new IllegalArgumentException("Wrong number of bytes for a private key, not 32 or 33");
+        }
+    }
+
+    /**
+     * Returns an ECKey created from this encoded private key.
+     */
+    public ECKey getKey() {
+        return ECKey.fromPrivate(bytes);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if(this == o) {
+            return true;
+        }
+        if(o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        if(!super.equals(o)) {
+            return false;
+        }
+        DumpedPrivateKey that = (DumpedPrivateKey) o;
+        return compressed == that.compressed;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(super.hashCode(), compressed);
+    }
+}

src/main/java/com/sparrowwallet/drongo/crypto/VersionedChecksummedBytes.java

@@ -0,0 +1,109 @@
+package com.sparrowwallet.drongo.crypto;
+
+
+import com.sparrowwallet.drongo.Utils;
+import com.sparrowwallet.drongo.protocol.Base58;
+import com.sparrowwallet.drongo.protocol.Sha256Hash;
+
+import java.io.Serializable;
+import java.util.Arrays;
+import java.util.Objects;
+
+/**
+ * <p>In Bitcoin the following format is often used to represent some type of key:</p>
+ * <p/>
+ * <pre>[one version byte] [data bytes] [4 checksum bytes]</pre>
+ * <p/>
+ * <p>and the result is then Base58 encoded. This format is used for addresses, and private keys exported using the
+ * dumpprivkey command.</p>
+ */
+public class VersionedChecksummedBytes implements Serializable, Cloneable, Comparable<VersionedChecksummedBytes> {
+    protected final int version;
+    protected byte[] bytes;
+
+    protected VersionedChecksummedBytes(String encoded) {
+        byte[] versionAndDataBytes = Base58.decodeChecked(encoded);
+        byte versionByte = versionAndDataBytes[0];
+        version = versionByte & 0xFF;
+        bytes = new byte[versionAndDataBytes.length - 1];
+        System.arraycopy(versionAndDataBytes, 1, bytes, 0, versionAndDataBytes.length - 1);
+    }
+
+    protected VersionedChecksummedBytes(int version, byte[] bytes) {
+        this.version = version;
+        this.bytes = bytes;
+    }
+
+    /**
+     * Returns the base-58 encoded String representation of this
+     * object, including version and checksum bytes.
+     */
+    public final String toBase58() {
+        // A stringified buffer is:
+        //   1 byte version + data bytes + 4 bytes check code (a truncated hash)
+        byte[] addressBytes = new byte[1 + bytes.length + 4];
+        addressBytes[0] = (byte) version;
+        System.arraycopy(bytes, 0, addressBytes, 1, bytes.length);
+        byte[] checksum = Sha256Hash.hashTwice(addressBytes, 0, bytes.length + 1);
+        System.arraycopy(checksum, 0, addressBytes, bytes.length + 1, 4);
+        return Base58.encode(addressBytes);
+    }
+
+    @Override
+    public String toString() {
+        return toBase58();
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if(this == o) {
+            return true;
+        }
+        if(o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        VersionedChecksummedBytes that = (VersionedChecksummedBytes) o;
+        return version == that.version && Arrays.equals(bytes, that.bytes);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = Objects.hash(version);
+        result = 31 * result + Arrays.hashCode(bytes);
+        return result;
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * This implementation narrows the return type to <code>VersionedChecksummedBytes</code>
+     * and allows subclasses to throw <code>CloneNotSupportedException</code> even though it
+     * is never thrown by this implementation.
+     */
+    @Override
+    public VersionedChecksummedBytes clone() throws CloneNotSupportedException {
+        return (VersionedChecksummedBytes) super.clone();
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * This implementation uses an optimized Google Guava method to compare <code>bytes</code>.
+     */
+    @Override
+    public int compareTo(VersionedChecksummedBytes o) {
+        int result =  Integer.compare(this.version, o.version);
+        Utils.LexicographicByteArrayComparator lexicographicByteArrayComparator = new Utils.LexicographicByteArrayComparator();
+        return result != 0 ? result : lexicographicByteArrayComparator.compare(this.bytes, o.bytes);
+    }
+
+    /**
+     * Returns the "version" or "header" byte: the first byte of the data. This is used to disambiguate what the
+     * contents apply to, for example, which network the key or address is valid on.
+     *
+     * @return A positive number between 0 and 255.
+     */
+    public int getVersion() {
+        return version;
+    }
+}