Trapdoor function
A trapdoor function is easy to compute in one direction but computationally difficult to invert without secret auxiliary information.
Hacking Cryptography
A trapdoor function is easy to compute but computationally difficult to invert without secret auxiliary information called a trapdoor.
- How it is used
- Supports asymmetric cryptography by making public computation reversible only with secret information.
- How deep it goes
- Defines forward computation and difficult inversion, then connects the idea to RSA factorization without developing other concrete functions.
- Examples
- Uses a dungeon trapdoor analogy and RSA multiplication-versus-factorization with large primes.
- What you can do after
- Understand why public-key operations can be easy to perform yet difficult to reverse without a private key.
Software Security for Developers
A mathematical function that is easy to compute in one direction but computationally infeasible to invert without special information.
- How it is used
- Supports public key encryption and digital signatures by making forward computation easy and reversal infeasible.
- How deep it goes
- Defines the one-way property with prime multiplication and names RSA and elliptic-curve problems without developing mathematical proofs.
- Examples
- Uses large-prime multiplication, RSA factoring, elliptic-curve discrete logarithms, and related key pairs.
- What you can do after
- Evaluate why public key systems can share public keys while requiring private keys to remain secret.
Read how Software Security for Developers explains trapdoor function →
Related concepts
- public key cryptographyused by · Public-key cryptography is asymmetric cryptography that uses mathematically related public and private keys for encryption, decryption, signing, and verification.
- bilinear pairingproduced by · A bilinear pairing is a map from two groups into a third group that preserves the group operation in each argument separately.
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