For example, Bitcoin Core encrypts your wallet using the Advanced Encryption Standard (AES). This is the same encryption algorithm used by the NSA for its classified information, and AES is considered extremely secure. Only wallets have encryption to protect private keys. Bitcoin Core specifically uses the AES-256-CBC because it's not known to be unsecure and is widely used.
Other wallets may choose to use other encryption schemes. Wallet encryption uses AES-256-CBC to encrypt only the private keys found in a wallet. The keys are encrypted with a master key that is completely random. This master key is then encrypted with AES-256-CBC with a key derived from the password using SHA-512 and OpenSSL's EVP_ByteToKey and a dynamic number of rounds determined by the speed of the machine performing the initial encryption (and updated according to the speed of a computer that later changes the passphrase).
Although the underlying code supports multiple encrypted copies of the same master key (and, therefore, several passphrases), the customer does not yet have a method for adding additional passwords. The first is symmetric encryption cryptography. Use the same secret key to encrypt the raw message at the source, transmit the encrypted message to the recipient, and then decrypt the message at the destination. A simple example is to represent alphabets with numbers, for example, A is 01, B is 02, etc.
A message such as “HELLO” will be encrypted as “0805121215” and this value will be transmitted over the network to the recipients. Once received, the recipient will decrypt it using the same inverse methodology 08 is H, 05 is E, etc., to obtain the value of the original “HELLO” message. Even if unauthorized people receive the encrypted message “0805121215”, it will have no value to them unless they know the encryption methodology. Many cryptocurrencies, such as Bitcoin, may not explicitly use such secret and encrypted messages, since most of the information related to Bitcoin transactions is largely public.
They include encryption functions and digital signatures that form an integral part of Bitcoin processing, even if Bitcoin doesn't directly use hidden messages. Governments, banks and the military aren't the only entities using AES-256 to protect their data. The algorithm described by AES is a symmetric key algorithm, which means that the same key is used to encrypt and decrypt the data. Cryptocurrencies such as Bitcoin and Ethereum have gained immense popularity thanks to their decentralized, secure and almost anonymous nature, which supports the peer-to-peer architecture and allows funds and other digital assets to be transferred between two different people without a central authority.
With the right quantum computer, AES-128 would take about 2.61*10^12 years to decipher, while AES-256 would take 2.29*10^32 years.