"HD wallets" stands for hierarchical deterministic wallets.
Decentralized digital wallets are used to manage users' private keys and assets while recording the digital assets on the blockchain.
In the early stage, such wallets had to back up the private key or the keystore whenever a new on-chain address was generated. With the emergence and mass adoption of industrial standards including BIP-32, the new generation of digital wallets, namely HD wallets, manages to streamline the process without compromising wallet security. Users can enjoy the convenience of creating nearly unlimited addresses from the same mnemonic, without the need to back up the private key or keystore of each address.
The principles behind HD wallets boil down to the following two steps:
First, the master private key is generated pseudorandomly, which is identical to how other types of wallets generate the private key.
Then, an unlimited number of child private keys are generated based on this master private key with a definitive and irreversible algorithm.
Why should the algorithm be definitive and irreversible?
Being "definitive" guarantees that all the child private keys can be derived from the master private key whilst being "irreversible" precludes the possibility of deriving the master private key reversely from the child private keys.
Hierarchical deterministic wallets are given the name because the derivation process of the private keys follows a tree structure, such that a master key can derive a sequence of child keys, each of which can derive a sequence of grandchild keys, and so on, to an infinite depth.
When users create their HD wallets on TronLink App for the first time, a mnemonic phrase will be generated. A mnemonic phrase is a list of words that can be used to create a seed that further derives all the private keys. This is why the mnemonic can be used to back up or recover the wallet.
The advantage of HD wallet lies in the fact that an unlimited number of new addresses can be derived from and controlled by the same mnemonic.
However, this feature can be a double-edged sword. Convenient as the HD wallet is, all the child private keys will be compromised once the mnemonic is exposed or leaked, putting your digital assets in extreme jeopardy.
Compared to HD wallets generated from mnemonics, non-HD wallets are imported via keystore files or private keys. Users can not generate more new addresses via non-HD wallets.
Non-HD wallets are labeled "Non-HD".
"Related wallets" in TronLink App refer to the addresses generated from the same mnemonic that is created or imported. These wallets share the same mnemonic and are thus related to each other. In TronLink App, such a set of addresses with the same mnemonic are called an "HD Wallet".
In the latest version of TronLink App, you can view the list of wallets related to your current wallet in "Wallet Management > Related Wallets". When creating a new wallet, the mnemonic of the current wallet will be used by default to create a new related wallet under the same HD wallet.
Under the same HD wallet, related wallets with different addresses distinguish themselves by the paths they use. If you customized the path when creating the address, please back it up together with the mnemonic!