Cryptographic primitives are the foundation of secure IT systems. This blogpost explains the most important methods and their significance in practice.
Cryptographic primitives are the foundational building blocks of modern IT security. They enable data to be transmitted confidentially, ensure the integrity of information, and verify digital identities. Without them, secure communication and trustworthy digital processes would be impossible. This article provides an overview of the most important primitives and their practical relevance.
Symmetric encryption uses the same secret key to encrypt and decrypt data. A widely used example is the Advanced Encryption Standard (AES), which today is the de facto norm for protecting sensitive information. Symmetric algorithms are highly efficient but only practical if both communication partners share the key in advance. In practice, they are therefore often combined with asymmetric methods.
Asymmetric encryption uses a key pair: a public key for encryption and a private key for decryption. The public key can be freely shared, while the private key remains secret. This makes it possible to communicate securely without having to exchange a password beforehand.
Algorithms such as RSA or Elliptic Curve Cryptography (ECC) make this possible. Because asymmetric methods are significantly slower than symmetric ones, they are mainly used to exchange a session key, which is then used for efficient symmetric data transmission.
Digital signatures ensure that messages remain unchanged and originate from the stated sender. The holder of a private key can sign a message, and anyone with the corresponding public key can verify the signature. Algorithms such as ECDSA or RSA signatures are widely used. A further benefit: the authorship of a message can be proven—even to third parties.
Hash functions map inputs of arbitrary length to outputs of fixed length. They are used for checksums, password hashes, or blockchain protocols. Well-known examples include SHA-256 and SHA-3.in.
A secure hash function must meet two key requirements:
MACs combine hash functions or block ciphers with a secret key. They ensure that a message is authentic and unaltered but can only be verified by parties who share the key.
Asymmetric methods are used to exchange the secret key for a symmetric algorithm. For example, Diffie–Hellman key exchange can be used to agree on a shared AES key to efficiently encrypt large volumes of data. In practice, this hybrid approach is implemented in protocols such as TLS.
The security of cryptographic algorithms depends heavily on key quality—keys should be indistinguishable from random bitstreams. Passwords are poor cryptographic keys, as their encoding introduces structure and predictability.
Key derivation functions transform passwords or other non-uniform inputs into strong cryptographic keys and often incorporate additional properties such as computational cost and memory usage to defend against brute-force attacks.
The security of cryptographic algorithms also depends on randomness. If secret keys can be guessed by brute force or predicted because they weren’t truly random, data cannot be protected. True random number generation (TRNG) is resource-intensive, so pseudo-random number generators (PRNGs) are often used. PRNGs expand a small random seed into a large sequence of bits suitable for cryptographic keys.
Without strong randomness, even robust algorithms can be broken.
Cryptographic primitives form the foundation of modern IT security. Their correct combination and secure implementation determine the trustworthiness of digital systems. While algorithms like AES, SHA-2, and ECDSA are currently considered secure, older methods such as DES or MD5 are no longer recommended. With emerging threats such as quantum computing, it is vital to stay up to date with new developments.
The recommendations above follow the current NIST cryptographic standards and guidelines.
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