Symmetric-Key Cryptography

    Pathik Bhattacharya
    Pathik Bhattacharya
    Published on November 10, 2022 3:23 PM

    Updated on January 16, 2023 1:42 PM

    Symmetric-key Cryptographic algorithms encrypt the plaintext and decrypt ciphertext using the same cryptographic keys.
    Symmetric-Key Cryptography
    Source: unsplash

    Encryption standards play a vital role in securing blockchain ecosystems from malware and unusual authentication or attacks. Generally, Cryptographic algorithms are used to protect the data within a blockchain which only could be accessed via keys. 

    These keys can be publicly shared or even act as private keys. In this section of basics, we are going to learn about Symmetric-key cryptography which is an algorithm for Blockchain encryption. Let’s dive deep into this.

    What is Symmetric-Key Cryptography?

    Symmetric-key Cryptography is a kind of encryption that uses a single key (a secret key) to encode and decode electronic data. The key must be exchanged between the organizations communicating using symmetric encryption so that it may be utilized in the decryption process. This encryption method is distinct from asymmetric encryption, which employs a pair of keys, one public and one private, to encrypt and decode messages.

    For example, we all have used Google docs (if not then use it once). The content we put on our doc file is only visible to us until we disable the sharing restrictions from the top right bar. When we opt for the “Share with anyone” feature, we get a link which then could be shared with a reliable person whom you wanted to get access to your doc file to see the content.

    Suppose the doc file is “Data or information” and the “link” is the key. This suffices the example of Symmetric-key cryptography.

    Encoding data in this manner has been widely utilized in earlier decades to permit covert communication between governments and armies.

    Symmetric-key cryptography is also known as shared-key cryptography, secret-key cryptography, single-key cryptography, one-key cryptography, and finally private-key cryptography. With this type of encryption, it is obvious that the key must be known by both the sender and the recipient. The distribution of the key is the source of the approach's intricacy.

    How Does Symmetric-Key Cryptography Work?

    Symmetric encryption technique ”scrambles” the data so that it cannot be understood by anybody who does not have the secret key to decode it. Once the intended receiver who holds the key obtains the message, the algorithm reverses its activity such that the message is restored to its original readable form. The secret key used by both the sender and the receiver might be a specific password/code or a random string of letters or numbers created using a secure random number generator (RNG).

    Source:  by David McNeal (TheCryptoWriter) | Medium

    The above diagram could be concluded as:

    • The sender encrypts their information with an encryption key (often a string of letters and numbers).

    • The encrypted information, known as ciphertext, appears as jumbled letters and is unreadable by anybody along the road.

    • The decryption key is used by the receiver to convert the ciphertext back into readable text.


    The previous example shows that the information was accessed using the same key.

    The data can only be viewed and accessed by these two parties (sender and recipient). This is why it is also known as secret key cryptography, private key cryptography, symmetric cryptography, and symmetric key encryption.

    The use of a single key for both encryption and decryption streamlines the encryption process. After all, you're using a single key to convert readable plaintext into unreadable gibberish (ciphertext) and vice versa. One benefit of employing symmetric encryption is that it enables data privacy and confidentiality without the additional complexity of many keys.

    For some applications, symmetric key encryption works on its own. It's handy for encrypting databases and files, for example, when no data is being sent openly between parties.

    Types of Symmetric Key Cryptography

    Symmetric Key cryptography is classified into two types:

    1. Block Algorithm

    2. Stream Algorithm

    Let’s understand both separately.

    Block Algorithm

    Block algorithms serve to secure electronic data blocks. While using the authorized private key, predefined set lengths of bits are changed. This key is then applied to every block. When encrypting network stream data, the encryption system stores the data in its memory components while waiting for the whole blocks. The amount of time the system waits can create a security hole and compromise data security and integrity. The solution to the problem comprises a method in which the data block can be lowered and merged with the contents of the preceding encrypted data block until the rest of the blocks emerge. This is referred to as feedback. Only once the complete block has been received it is then marked as encrypted.

    Stream Algorithm

    Stream algorithms are not stored in the memory of the encryption system but instead come in data stream algorithms. This approach is deemed slightly safer since a disk or system does not preserve data without encryption in the blocks.

    Some examples of Symmetric-Key Cryptography:

    • AES (Advanced Encryption Standard)

    • DES (Data Encryption Standard)

    • IDEA (International Data Encryption Algorithm)

    • Blowfish (Drop-in replacement for DES or IDEA)

    • RC4 (Rivest Cipher 4)

    • RC5 (Rivest Cipher 5)

    • RC6 (Rivest Cipher 6)

    AES, DES, IDEA, Blowfish, RC5 and RC6 are block ciphers. RC4 is a stream cipher.

    Significance of Symmetric-Key Cryptography

    Despite being an older kind of encryption, symmetric encryption is quicker and more effective than asymmetric encryption, which strains networks owing to performance concerns with data quantity and high CPU usage. 

    Symmetric cryptography is generally used for bulk encryption / encrypting huge volumes of data, such as for database encryption, due to its greater performance and faster speed (relative to asymmetric encryption). 

    The secret key could only be accessible to the database itself to encrypt or decrypt in the event of a database. Comparing existing standards for asymmetric algorithms to industry-standard symmetric encryption, one can see that the latter is less susceptible to developments in quantum computing (at the time of writing).

    Here are some instances in which symmetric cryptography is applied:

    • Applications for making payments, like card transactions, require the protection of PII to stop identity theft and fraudulent charges.

    • validations that a message's sender is who they say they are.

    • Hashing or the random number generation.

    In addition to encryption, symmetric ciphers are frequently employed to accomplish other cryptographic primitives.

    A message cannot be guaranteed to remain intact while being encrypted. As a result, a message authentication code is frequently appended to a ciphertext to make sure that the recipient will be aware of modifications to the ciphertext. From an AEAD cipher, message authentication codes may be created (e.g. AES-GCM).

    However, without involving extra parties, symmetric ciphers cannot be employed for non-repudiation (the assurance that someone cannot deny the validity of something) reasons.

    Key Differences Between Symmetric and Asymmetric Cryptography


    Symmetric-Key Cryptography

    Asymmetric-Key Cryptography

    Symmetric encryption uses a single key that must be shared with the individuals who need to receive the message.

    While, Asymmetrical encryption involves a pair, consisting of a public key and a private key, to encrypt and decode messages while communicating

    An old concept

    Relatively new concept

    In symmetric cryptography, data is encrypted or decrypted using a single shared key that both parties are aware of.

    Asymmetric encryption is developed to address the issue of the symmetric encryption model's requirement for key exchange by replacing the key with a pair of public-private keys.

    The execution time is much faster

    Slower execution time.



    The most recent technologies could sometimes be the ideal fit when it comes to encryption.  In reality, as cryptography develops in a new way, new protocols are being built to keep up with would-be hackers and to safeguard the data to increase privacy. In the upcoming years, hackers will inevitably make things difficult for specialists, thus we can confidently anticipate new advancements from the cryptography community.