Cryptography
From Caesar's cipher to post-quantum: keys, signatures, TLS and timestamps.
Block cipher modes of operation: ECB, CBC, CTR and GCM
Why AES alone is not enough: how the ECB, CBC, CTR and GCM modes work, what IVs and nonces are, and why authenticated encryption is the right choice.
Blockchain explained from a cryptographic perspective
Chained hashes, Merkle trees, digital signatures and proof of work: the cryptographic ingredients of a blockchain, and why its data is not encrypted.
Common cryptography mistakes and how to avoid them
Base64 mistaken for encryption, keys in code, reused nonces, unverified certificates: the most frequent cryptography mistakes and what to do instead.
Cryptographic hash functions: what they are and what they do
What a cryptographic hash is, which properties it needs, why MD5 and SHA-1 are obsolete and how SHA-256 protects files, signatures and evidence.
Cryptographic key management: the real weak point
Generating, storing, rotating and destroying cryptographic keys: the key life cycle, HSMs, envelope encryption and mistakes that defeat encryption.
Diffie-Hellman: the key exchange explained simply
How two people can agree on a secret key while talking in public: the Diffie-Hellman exchange with a worked example, its limits and modern versions.
Digital certificates and certificate authorities explained
What an X.509 certificate is, how the certificate authority chain of trust works, what revocation and Certificate Transparency are and why they matter.
Disk encryption: BitLocker, FileVault and LUKS compared
How full-disk encryption works with BitLocker, FileVault and LUKS, what it protects when the computer is off and why the recovery key is critical.
Electronic signatures and eIDAS: simple, advanced, qualified
The three levels of electronic signature under eIDAS explained from a technical angle: requirements, devices, qualified certificates and examples.
Elliptic curve cryptography: why short keys are enough
How elliptic curve cryptography works, why a 256-bit key matches 3072-bit RSA, and where you meet it every day: HTTPS, encrypted chats and Bitcoin.
End-to-end encryption in chat apps: how it works and its limits
What end-to-end encryption really means in messaging apps, how the Signal protocol works, what safety numbers are for and where the remaining risks lie.
Forward secrecy: why it protects your past communications
What forward secrecy is, why a stolen private key must not expose traffic recorded in the past, and how TLS and encrypted messaging apps achieve it.
Hardware security keys and smart cards: how they work
How FIDO2 keys, passkeys and smart cards hold a private key that cannot be copied, why they resist phishing and how to use them without getting locked out.
History of cryptography: from Caesar to Enigma and beyond
From the Caesar cipher to Enigma and public-key cryptography: how modern cryptography was born and which lessons its history still teaches users today.
AES explained simply: how the encryption standard works
What AES is, how it transforms data in 128-bit blocks, how 128-bit and 256-bit keys differ, and why it is still the most widely used encryption standard.
Digital signatures: how they really work, step by step
What happens when you digitally sign a file: hash, private key, certificate and verification. How it differs from a scanned signature; p7m and PDF.
RSA: how public-key cryptography works
RSA explained with a numerical example: prime numbers, public and private keys, why factoring is hard and which mistakes leave RSA open to attack.
Password hashing: bcrypt, scrypt and Argon2 compared
Why passwords are not encrypted but run through slow functions: salt, cost factor and the differences between bcrypt, scrypt, PBKDF2 and Argon2.
PGP and GnuPG: encrypting and signing email with care
How PGP works with GnuPG: key pairs, fingerprints, web of trust, signing and encrypting email. What it protects, what it does not, mistakes to avoid.
Post-quantum cryptography: what changes and why it matters now
Why quantum computers threaten RSA and elliptic curves, which post-quantum algorithms have been standardised and how to prepare for the transition.
Random numbers in cryptography: why randomness matters
Keys, nonces and salts depend on randomness: true versus pseudorandom generators, entropy sources and what really happens when randomness is weak.
Steganography vs cryptography: hiding versus making unreadable
How steganography differs from cryptography, from invisible inks to image bits, digital watermarks and how hidden messages can actually be detected.
Symmetric vs asymmetric cryptography: differences and uses
A shared key or a key pair? How symmetric and asymmetric cryptography work, their strengths and limits, and why real-world systems use them together.
TLS and HTTPS: what really happens behind the padlock
What TLS does behind the HTTPS padlock: handshake, key exchange, certificate checks and data encryption. What it really protects and what stays visible.
Trusted timestamps: how to prove when a document existed
How a cryptographic timestamp works: hash, time stamping authority and signed token. What it is used for, what it really proves and its limits.