## 2 Foundations of Blockchain, Ethereum, Smart Contracts, and Digital Wallets
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Digital Wallet** & **Cryptocurrency Wallet** \\ \hline \multirow{3}{*}{Goal} & Holds various forms of digital payment options, & \multirow{3}{*}{Specifically designed for storing, sending, and \multirow{3}{*}{receiving cryptocurrencies.} \\  & such as credit and debit cards, electronic money, & \\  & and occasionally cryptocurrencies. & \\ \hline \multirow{2}{*}{Types of assets} & Supports loyalty cards, tickets, digital IDs, and & Only manages cryptocurrencies and \multirow{2}{*}{blockchain-based assets.} \\  & sometimes cryptocurrency. & \\ \hline \multirow{2}{*}{Connection} & Typically linked to traditional financial & \multirow{2}{*}{Connected to blockchain networks, with private} \\  & institutions (banks, payment networks). & and public key management. \\ \hline \multirow{2}{*}{Examples} & Apple Pay, Google Pay, PayPal & MetaMask, Argent, Trust Wallet, \\  & & Coinbase Wallet \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Digital wallets vs. Cryptocurrency wallets. how cryptographic keys are stored and managed [22]. Users may retain full control over their keys or delegate key storage to an external service provider. Based on this distinction, cryptocurrency wallets can be classified into the following types:  
1. Hardware wallets (cold storage)--type of non-custodial wallet that exists as physical devices designed for secure offline storage of cryptographic keys. Since they operate offline (cold storage) mode, they are highly resistant to cyber threats such as phishing, malware, and hacking attempts [22]. Due to their enhanced security features, hardware wallets are considered the safest option for storing cryptocurrencies. Some of the most popular models include Ledger Nano S or X [23], and Trezor Model T or One [24]. 2. Web-based wallets (hot wallets)--web wallets provide access via a web browser, making them convenient for everyday transactions. However, private keys are often managed by a third-party service, which means that users must trust the provider for security. Although these wallets offer easy access and usability, they introduce higher security risks, as they remain online (hot storage) and are vulnerable to hacking attempts. An example of this type of wallet is MetaMask. 3. Mobile-based wallets--smartphone applications that allow users to store and manage cryptocurrencies conveniently. They are designed for on-the-go transactions and often include QR code support for seamless payments. Although they provide greater accessibility, mobile wallets can be vulnerable to device theft, malware, or unauthorized access if proper security measures (for example, biometric authentication, PIN protection) are not in place. Examples of popular mobile wallets include AlphaWallet [25] or Trust Wallet. 4. Desktop wallets--software applications installed on a personal computer. Unlike web wallets, desktop wallets do not require a constant internet connection, reducing the risk of remote attacks. They provide users with full control over their private keys, but the security of the wallet depends on the computer's protection against malware and viruses. Examples of popular desktop wallets include Electrum (Bitcoin wallet) [26] or Atomic Wallet [27]. 5. Paper wallets--paper wallets involve physically printing or writing down private and public keys on paper. Since keys never exist in digital form, they are immune to cyber-attacks. However, this method introduces new risks, such as loss, damage, or theft of the physical document. Although paper wallets provide strong security against hacking, they require careful handling to prevent destruction or unauthorized access. The choice of wallet type depends on security requirements, accessibility preferences, and user experience. Although hardware and paper wallets offer maximum security, they may not be convenient for frequent transactions. However, web, mobile, and desktop wallets provide easier access, but require additional security precautions.