Cryptography

Definition

Cryptography is the practice of securing communication so that the content being sent is only visible to the sender and the intended recipient.

A modern cryptographic system has four main goals:

• Confidentiality: Information can never be disclosed to someone who is not authorized to see it.
• Identification and Authentication: Before any information is exchanged, identify and then authorize both the sender and the recipient.
• Integrity: Information must not be modified in storage or transit. Any modification must be detectable.
• Non-repudiation: Cannot disclaim the creation/transmission of the message. This provides “digital” legitimacy and traceability of a transaction.

Current cryptographic systems provide all the above or a combination of the above in various forms for an intended application.

What is cryptography used for?

Cryptography is used everywhere in our daily lives. Each time you make an online purchase, conduct a banking transaction, or ping your email client, cryptography is working in the background. It secures all transmitted information in our IoT world to authenticate people and devices, and devices to other devices.

What are the types of cryptography?

Symmetric keys and asymmetric keys are two basic types of algorithms that are used in modern cryptography. Symmetric algorithms use only private keys (commonly referred to as secret keys) while asymmetric key algorithms use a combination of private and public keys.

Symmetric cryptography (secret key)- In symmetric key cryptography, the sender and receiver share a secret key. That key has to be securely agreed upon before the actual message is sent. To send a message, the sender processes plaintext data using an encryption algorithm under the control of the secret shared key. The result is ciphertext, a scrambled set of data that's useless without knowledge of the key. The encryption algorithm itself is not secret and, in most cases, is publicly known. Once the ciphertext is created, it can be transmitted on a public channel. The recipient then applies the ciphertext and the secret shared key to the decryption algorithm, and the original plaintext is recovered. The encryption algorithms are designed so that even similar messages or similar keys will produce wildly divergent ciphertexts.

Asymmetric cryptography (public key)- In asymmetric cryptography, one party (usually the recipient) employs a mathematical algorithm to create a pair of different but cryptographically related keys. The recipient sends one of the keys, designated the public key, to the sender, using an insecure public channel (such as the internet). The sender gets the public key, and uses it along with a publicly known algorithm to encrypt the plain text message. The result is ciphertext. Unlike symmetric encryption, in which the secret shared key has to be kept secret, the public key in an asymmetric cipher is published to everyone, and the public encryption key provides no clue about how to decrypt the message. When the recipient gets the ciphertext message, they recover the plain text message using a decryption algorithm and the private decryption key.