Cryptography and blockchain are two inextricably linked technologies that play a key role in providing security and trust in the digital world. Cryptography secures data, while blockchain uses these techniques to create decentralized and immutable records. In this article, we will look at the basic concepts of cryptography and their application in blockchain.

Cryptography, as the science of information security, has been around for several millennia. Its methods and algorithms are constantly evolving to face new threats and attacks. In today’s world, cryptography is used everywhere, from protecting email to securing financial transactions. Blockchain, in turn, is a distributed database in which information is stored as a chain of blocks. Each block contains the data and hash of the previous block, making the system resistant to changes and attacks.

Basic cryptographic concepts

Cryptography is the science of protecting information by converting it into an unreadable format. The basic concepts of cryptography include:

• Encryption: the process of converting data into ciphertext that can only be read using a key. Encryption can be symmetric and asymmetric. Symmetric encryption uses the same key to encrypt and decrypt data. Asymmetric encryption uses two different keys: a public key and a private key;
• Decryption: the process of converting encrypted text back to its original format. Decrypting data requires the key that was used to encrypt it. In the case of asymmetric encryption, a private key is used for decryption;
• Hashing: the process of converting data into a fixed string size that uniquely identifies the original data. Hash functions are used to verify data integrity and create digital signatures. It is important to note that hashing is an irreversible process, meaning that it is impossible to recover the original data from the hash;
• Digital signatures: a method of verifying the authenticity and integrity of data using cryptographic keys. Digital signatures are created using a private key and verified using a public key. They provide authentication of the sender and protection against data tampering.

Hashing and its role in blockchain

Hashing plays a key role in blockchain by ensuring the security and immutability of data. Key aspects of hashing include:

• Hashing algorithms: such as SHA-256, which are used to create unique hashes of data. Hashing algorithms should be collision resistant, meaning the probability of getting the same hash for different data should be extremely low;
• Immutability: changing even a single character in the original data results in a completely different hash. This property of hash functions ensures data integrity and allows any changes to be detected;
• Blockchain: Each block in the blockchain contains a hash of the previous block, creating a chain that is protected from change. If someone tries to change the data in one block, they will have to change the hashes of all subsequent blocks, which requires huge computational resources.

Asymmetric encryption and digital signatures

Asymmetric encryption uses a pair of keys: a public key and a private key. These keys play an important role in providing security and authentication in the blockchain.

Public key: used to encrypt data and verify digital signatures. The public key can be freely distributed as it does not allow decryption of data.

Private key: used to decrypt data and create digital signatures. The private key must be kept secret, as compromising it can lead to loss of data confidentiality and forgery of digital signatures.

Digital signatures ensure the authenticity and integrity of the data. Example: when you send a transaction on a blockchain, you sign it with your private key. The recipient can use your public key to verify the signature and ensure that the transaction really comes from you. This prevents transactions from being tampered with and ensures that it was you who sent it.

Cryptography is the foundation of security and trust in blockchain. Understanding basic cryptographic concepts and their application to blockchain will help you better understand how these technologies work and how they can be used to create secure and trustworthy systems. It is important to note that cryptography and blockchain continue to evolve, and new methods and algorithms are constantly being developed to improve the security and efficiency of these technologies.