Non-Repudiation Flashcards

Cannot deny an action you performed. Combines proof of integrity + proof of origin. Like signing a contract — you can't deny your signature.

Mathematical algorithm converting any data into a fixed-length hash value. Any change to input = completely different output. One-way function (cannot reverse-engineer data from hash).

Another name for a hash value. The fixed-length fingerprint output of a hash function.

Evidence that data has not been changed. Achieved by hashing. If received hash = original hash, data is unchanged. Does NOT prove sender identity.

Evidence that data came from a specific sender. Achieved by digital signatures using the sender's private key. Anyone can verify with the public key.

Hash encrypted with sender's PRIVATE key. Attached to the plaintext message. Receiver decrypts with sender's PUBLIC key and compares hashes. Proves both integrity and origin.

The SECRET key used to CREATE (sign) a digital signature. Held only by the sender. No one else can produce the same signature.

The SHARED key used to VERIFY a digital signature. Available to anyone. Cannot be used to create a valid signature — only to check one.

NO. Hashing only proves data hasn't changed. It doesn't link the data to any specific person. You need a digital signature for sender identification.

NO. The plaintext can be sent as-is. The digital signature (encrypted hash) is attached separately. Non-repudiation works on unencrypted messages.

The resulting hash is completely different. Even a single bit change produces an entirely different hash output — making tampering immediately detectable.

When two different inputs produce the same hash. A weakness in older algorithms (MD5, SHA-1). Modern algorithms (SHA-256) make collisions computationally infeasible.

Trusted entity that issues and signs digital certificates, binding a public key to a verified identity. Enables trust in digital signature systems at scale.

Two mathematically related keys (public + private). What one encrypts, only the other decrypts. Basis for digital signatures. Private key signs, public key verifies.

Proof of ORIGIN — who sent the data. Integrity tells you data wasn't changed. Non-repudiation adds: and it came from THIS specific person, who cannot deny it.

8.1MB encyclopedia file. Change ONE character → completely different hash. Same file size, impossible to spot manually, but instantly detected by hash comparison. Demonstrates hash sensitivity.