# 9.4 Cryptographic Foundations
PTERI relies only on **well-established cryptographic primitives**.
There are no experimental algorithms.
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#### Key Generation & Signing
* Elliptic Curve Cryptography (secp256k1)
* Hardware-backed key storage where available
* Keys are generated locally on the device
* Private keys are non-exportable
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#### Challenge–Response Authentication
* Cryptographically random nonces
* Explicit expiration windows
* Single-use enforcement
* Deterministic verification
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#### Transaction Verification
* Litecoin proof-of-work consensus
* UTXO-based validation
* Optional MWEB privacy guarantees
* Public, independently verifiable settlement
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#### Hashing & Integrity
* Cryptographic hash functions for message integrity
* Signed payloads are tamper-evident
* Any modification invalidates verification
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