Overview
PBKDF2 makes password guessing more expensive by applying many HMAC-like rounds to a password and salt before producing key material.
CoreSource checked
PBKDF2
Derives keys from passwords by iterating a pseudorandom function with a salt.
Quick Facts
Compact metadata for implementation and discovery.
- Category
- Cryptography
- Difficulty
- Intermediate
- Family
- Key Derivation
- Tier
- Core
- Status
- Verified
- Review
- Source Checked
- Sources
- 1
- Formulas
- 1
- Relationships
- 6
- Code example
- Ready
- Visualization
- Ready
Core Concepts
saltiteration countpseudorandom functionkey stretchingmisuse resistanceparameter validation
Quick facts
Complexity
Runtime and memory behavior at a glance.
Best
O(iterations)
Average
O(iterations)
Worst
O(iterations)
Space
O(1)
When to Use
- Use when protecting messages needs salt.
- Use when the input matches the assumptions behind key Derivation.
When Not to Use
- Avoid when a well-reviewed library already provides the primitive for production use.
- Avoid when a simpler algorithm gives the required result with less setup.
What It Does
- Derives keys from passwords by iterating a pseudorandom function with a salt
- Uses salt and iteration count to guide the work.
- Produces ciphertext, digest, proof, or derived key.
Use Cases
- Protecting messages
- Authenticating data
- Deriving or managing cryptographic material
Inputs
- Secret key or public parameters
- Message or secret data
- Nonce, salt, or context where needed
Outputs
- Ciphertext, digest, proof, or derived key
Key Formulas (1)
PBKDF2 block
Ti = U1 xor U2 xor … xor Uc
T_i = U_1 xor U_2 xor ... xor U_cCombines repeated PRF outputs for one derived-key block.
Pseudocode
- 1.Validate keys, nonces, salts, group parameters, and input ranges
- 2.Apply the primitive's block, hash, group, or reduction operation
- 3.Combine intermediate values exactly as the construction specifies
- 4.Return the protected value, proof, signature, derived key, or verification result
Canonical Example
- Input
- message = 'pay 10' with configured keys, nonces, or public parameters
- Output
- Ciphertext, digest, proof, or derived key
- Explanation
- PBKDF2 applies salt to produce ciphertext, digest, proof, or derived key.
Implementation Notes
- Use constant-time library implementations for real systems instead of hand-written primitives.
- Keep the salt step separate enough to test independently.
- Use reviewed libraries and protocol specifications for production security-sensitive code.
Common Pitfalls
- Reusing nonces, salts, pads, or domain parameters can destroy the intended security property.
- Test edge cases, not only clean examples.
- Treating educational pseudocode as production crypto can hide nonce, parameter, and side-channel requirements.
Interactive Mechanism Walkthrough
Graph Frontier & Edge RelaxationShow the major cryptographic rounds or data dependencies without exposing secrets.
Step 1 of 4: Validate keys, nonces, salts, group parameters, and input ranges
cryptography-mechanismNotes
PBKDF2 depends heavily on salt quality, pseudorandom function choice, and an iteration count appropriate for the deployment environment.
Sources (1)
What each reference supports for this entry.
Explore Next
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Both derive keys from passwords with different resistance properties.
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Both are password-based key derivation functions.
Compare with thisRelationships
View full relationship pageTags
CryptographyKey DerivationPassword HashingMessage Authentication