What does an encryption key determine in a cryptographic algorithm?

The encryption key plays a crucial role in determining the output of a cryptographic algorithm. In the context of encryption, the key acts as a parameter that influences how the plaintext data is transformed into ciphertext. This transformation relies entirely on the key's value and characteristics; changing the key will lead to a different output even if the input remains the same.

Cryptographic algorithms use keys in a manner that provides confidentiality, ensuring that without the correct key, the output (ciphertext) cannot be reverted back to the original data (plaintext) by an unauthorized party. This essential aspect of cryptography makes the encryption key fundamental for the security of the data being encrypted.

While methods of data backup, storage locations, and data transmission speeds can be relevant to data security and management, they do not interact with the cryptographic processes directly as the output does. Thus, the role of the encryption key is specifically tied to how it generates the resulting encrypted information, confirming that the selection of the output of the cryptographic algorithm is indeed the right choice.