What type of encryption allows data to be processed without decrypting it first?

Homomorphic encryption is a specialized form of encryption that enables computations to be performed on ciphertexts, which are encrypted data, without requiring access to the underlying plaintext data. This means that operations such as addition and multiplication can be carried out on the encrypted data, and the result, when decrypted, will match the outcome of operations performed on the plaintext data.

This type of encryption is particularly valuable in scenarios where data privacy is crucial, such as in cloud computing or in cases where sensitive data needs to be processed by third parties. It allows for data analysis and processing without exposing the actual data to those performing the computations, thereby maintaining data confidentiality.

In contrast, lightweight cryptography focuses on providing secure encryption for resource-constrained environments, such as IoT devices, but does not inherently allow for operations on encrypted data. Stream ciphers and block ciphers are traditional forms of encryption that require data to be decrypted before processing it, which does not meet the requirement described in the question.