What Is an Encryption Key?
An encryption key is a digital value that controls how data is locked or unlocked. Learn why a secret key needs protection.
Free video lesson · 1:20
What Is an Encryption Key?
Quantum Computing & Encryption for Beginners
Music: “Thinking Music” by Kevin MacLeod. Creative Commons Attribution 4.0.
A key is the value that controls an encryption operation; the example uses one shared secret key.
Read the video transcript
An encryption key is a digital value used to lock or unlock data. It is not a metal key. It is information that your software uses when it scrambles a message or makes it readable again.
Imagine two friends using a system where they share the same secret key. One friend uses it to scramble a message. The other uses the same key to read that message.
The instructions for scrambling can be public. Knowing those instructions should not be enough to read the message. You also need the right key, just as knowing how a lock works does not give you its key.
If someone steals the secret key, they may be able to read the messages it protects. That is why protecting a key matters as much as choosing good encryption. A strong lock is little help if someone copies its key.
This example uses one shared secret. Other systems use two different keys that work together. The job of a key depends on the system, so not every digital key needs to be kept secret.
How can one key be public? Watch What Is Public-Key Cryptography? To see one widely used shared-key method, watch Is AES-256 Quantum Safe?
The short answer
An encryption key is a digital value used to lock or unlock data. It is not a metal key. It is information that your software uses when it scrambles a message or makes it readable again.
A simple example
Imagine two friends using a system where they share the same secret key. One friend uses it to scramble a message. The other uses the same key to read that message.
The instructions for scrambling can be public. Knowing those instructions should not be enough to read the message. You also need the right key, just as knowing how a lock works does not give you its key.
If someone steals the secret key, they may be able to read the messages it protects. That is why protecting a key matters as much as choosing good encryption. A strong lock is little help if someone copies its key.
This example uses one shared secret. Other systems use two different keys that work together. The job of a key depends on the system, so not every digital key needs to be kept secret.
Why protect the key?
Think about a locked box sitting beside its key. A strong lock helps very little if someone can take both. Software needs to protect secret keys separately from the encrypted information they unlock.
Check your understanding
Is changing a filename the same as changing an encryption key?
Answer
No. A filename is a label. A key is a value used by the encryption mathematics.
Keep learning
Follow the free video course one question at a time. For help applying these ideas at work, explore team training or a cryptography audit.