The process of transforming encrypted data back into a format that is readable by a user or machine.

What Is Decryption?

Encryption is used to protect sensitive data from bad actors, and to ensure that it is difficult to view or understand in the event that it is stolen. There are many reasons why a party might wish to encrypt data, such as for transmitting credit card details or user passwords.

Cryptography is at the heart of many parts of the internet and of wider digital communication. It is most commonly concerned with disguising readable information (known as plaintext) as unreadable ciphertext through the process of encryption. 
A range of systems are available to accomplish this — using cryptographic algorithms — where plaintext is fed in order to create encrypted data, and fed back in order to be decrypted.
In the cryptocurrency sector, the most commonly used form of cryptography is known as public key or asymmetric key encryption. In this system, pairs of keys are used to encrypt and decrypt information. On the Bitcoin blockchain, encryption and decryption is carried out through the Elliptical Curve Digital Signature Algorithm (ECDSA).

Cryptographers are preoccupied with the strength of their cryptographic systems. Algorithms are designed to be practicably impossible for a real adversary to crack. 

There are some algorithms that are referred to as information-theoretically secure, meaning they can be proven to be unbreakable even with theoretically unlimited computing power. However, in reality these systems are extremely difficult (often more or less impossible) to actually implement. 

As a result, most cryptographic systems currently used are known as computationally secure.

Although it is theoretically possible to break them, it would not be practical for an actual bad actor to do so.