#213 rough sketch of needed functionality as a discussion basis

hd-wallet/specification.md

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+# HD Wallet integration specification
+
+## Motivation 
+
+Hierarchical deterministic wallets are a common practice in blockchains like Bitcoin and Cardano.
+The idea behind that is to derive multiple keys (private and public) and addresses from a master key.
+The advantage in contrast to individual addresses is that these keys/addresses are linked together through the master key.
+Thus it is possible to maintain privacy due to changing public addresses frequently.
+Otherwise one could track users through various transactions. 
+
+Therefore it must be possible for users to use this concept via an easy-to-use API within this library.
+
+## Implementation
+
+- HDWallet Class
+  - Wrapper for Account - Deriving new Accounts with one Mnemonic
+  - Scanning strategy -> 20 consecutive empty addresses
+  - First Interface Approach [HDWalletInterface.java](src/main/java/com/bloxbean/cardano/hdwallet/HDWalletInterface.java)
+- Transaction Building - extend QuickTxBuilder to use HDWallet
+  - Getting UTXOs to pay certain amount
+  - Getting Signers for the respective UTXOs spend in the transaction
+  - Build and Sign Transactions from HDWallet
+- Minting Assets to a specific address 
+- Coin Selection Strategies 
+  - Support common UTXO SelectionStrategys (Biggest, sequential, ...)

hd-wallet/src/main/java/com/bloxbean/cardano/hdwallet/HDWalletInterface.java

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+package com.bloxbean.cardano.hdwallet;
+
+import com.bloxbean.cardano.client.account.Account;
+import com.bloxbean.cardano.client.api.model.Amount;
+
+import java.util.List;
+
+public interface HDWalletInterface {
+
+    private String mnemonic = "";
+
+//    public HDWalletInterface(Network network, String mnemonic);
+//    public HDWalletInterface(Network network);
+
+    // sum up all amounts within this wallet
+    // scanning strategy is as described in specification.md
+    public List<Amount> getWalletBalance();
+
+    /**
+     * Returns the account for the given index
+     * @param index
+     * @return
+     */
+    public Account getAccount(int index);
+
+    /**
+     * Creates a new Account for the first empty index.
+     * @return
+     */
+    public Account newAccount();
+
+    /**
+     * Returns the stake address
+     * @return
+     */
+    public String getStakeAddress();
+
+    /**
+     * returns the master private key
+     * @return
+     */
+    public byte[] getMasterPrivateKey();
+
+    /**
+     * Returns the master public key
+     * @return
+     */
+    public String getMasterPublicKey();
+
+    /**
+     * returns the master adress from where other addresses can be derived
+     * @return
+     */
+    public String getMasterAddress(); // prio 2
+
+}