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ZK Compression

ZK Token Proof Program

A native Solana program that verifies zero-knowledge proofs used by Token-2022's Confidential Transfers extension. It validates range proofs (proving encrypted amounts are non-negative and within bounds), equality proofs (proving two ciphertexts encrypt the same value), and ciphertext validity proofs required for confidential token operations. The program uses ElGamal encryption over Ristretto255 and Bulletproofs for range verification, enabling private token transfers where balances and amounts remain encrypted on-chain.

IDzk-token-proof-program
Plain meaning

Plain meaning

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A native Solana program that verifies zero-knowledge proofs used by Token-2022's Confidential Transfers extension. It validates range proofs (proving encrypted amounts are non-negative and within bounds), equality proofs (proving two ciphertexts encrypt the same value), and ciphertext validity proofs required for confidential token operations. The program uses ElGamal encryption over Ristretto255 and Bulletproofs for range verification, enabling private token transfers where balances and amounts remain encrypted on-chain.

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Technical context

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Compressed state, proofs, and scale-oriented storage patterns.

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ZK Token Proof Program (zk-token-proof-program)
Category: ZK Compression
Definition: A native Solana program that verifies zero-knowledge proofs used by Token-2022's Confidential Transfers extension. It validates range proofs (proving encrypted amounts are non-negative and within bounds), equality proofs (proving two ciphertexts encrypt the same value), and ciphertext validity proofs required for confidential token operations. The program uses ElGamal encryption over Ristretto255 and Bulletproofs for range verification, enabling private token transfers where balances and amounts remain encrypted on-chain.
Related: ElGamal Encryption, Zero-Knowledge Proofs (ZKP), Token-2022 (Token Extensions)
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Branch

ElGamal Encryption

ElGamal encryption is a public-key cryptosystem based on the Diffie-Hellman problem over an elliptic curve group, providing additive homomorphism — meaning the encryption of a sum of values equals the product of their individual ciphertexts — which makes it suitable for confidential token balance accounting where balances can be updated without decrypting them. On Solana, the Token-2022 Confidential Transfers extension uses Twisted ElGamal encryption over the Ristretto255 curve to encrypt token balances in token accounts, so transfers update encrypted balances homomorphically while zero-knowledge range proofs (proving a balance is non-negative and a transfer amount is within bounds) prevent overdrafts without revealing any amounts. Each confidential token account stores a pending encrypted incoming balance and an available encrypted balance, and the account owner uses their ElGamal private key to decrypt and rotate balances via ZK-proof-accompanied instructions.

Confidential Transfers
Open term
Branch

Zero-Knowledge Proofs (ZKP)

A zero-knowledge proof is a cryptographic protocol by which a prover convinces a verifier that a statement is true — for example, that a state transition is valid — without revealing any information beyond the truth of the statement itself, satisfying the properties of completeness, soundness, and zero-knowledge. In Solana's ecosystem, ZKPs are used by ZK Compression (via Groth16 SNARKs) to prove correct state transitions for compressed accounts without storing full account state on-chain, and by the Token-2022 Confidential Transfers extension (via ElGamal encryption and range proofs) to prove token balances are non-negative without revealing the actual amounts. Solana's BPF VM exposes the alt_bn128 elliptic curve syscall to make on-chain Groth16 proof verification computationally feasible within the 1.4M compute unit budget.

Groth16PLONK
Open term
Branch

Token-2022 (Token Extensions)

The next-generation token program (TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb) that extends SPL Token with configurable extensions. Extensions include transfer fees, confidential transfers, transfer hooks, permanent delegate, non-transferable tokens, interest-bearing tokens, metadata, and more. Token-2022 is backwards-compatible with SPL Token for basic operations.

SPL Token ProgramTransfer Hook
Open term
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ZK Compression

ElGamal Encryption

ElGamal encryption is a public-key cryptosystem based on the Diffie-Hellman problem over an elliptic curve group, providing additive homomorphism — meaning the encryption of a sum of values equals the product of their individual ciphertexts — which makes it suitable for confidential token balance accounting where balances can be updated without decrypting them. On Solana, the Token-2022 Confidential Transfers extension uses Twisted ElGamal encryption over the Ristretto255 curve to encrypt token balances in token accounts, so transfers update encrypted balances homomorphically while zero-knowledge range proofs (proving a balance is non-negative and a transfer amount is within bounds) prevent overdrafts without revealing any amounts. Each confidential token account stores a pending encrypted incoming balance and an available encrypted balance, and the account owner uses their ElGamal private key to decrypt and rotate balances via ZK-proof-accompanied instructions.

Open term
ZK Compression

Zero-Knowledge Proofs (ZKP)

A zero-knowledge proof is a cryptographic protocol by which a prover convinces a verifier that a statement is true — for example, that a state transition is valid — without revealing any information beyond the truth of the statement itself, satisfying the properties of completeness, soundness, and zero-knowledge. In Solana's ecosystem, ZKPs are used by ZK Compression (via Groth16 SNARKs) to prove correct state transitions for compressed accounts without storing full account state on-chain, and by the Token-2022 Confidential Transfers extension (via ElGamal encryption and range proofs) to prove token balances are non-negative without revealing the actual amounts. Solana's BPF VM exposes the alt_bn128 elliptic curve syscall to make on-chain Groth16 proof verification computationally feasible within the 1.4M compute unit budget.

Open term
Token Ecosystem

Token-2022 (Token Extensions)

The next-generation token program (TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb) that extends SPL Token with configurable extensions. Extensions include transfer fees, confidential transfers, transfer hooks, permanent delegate, non-transferable tokens, interest-bearing tokens, metadata, and more. Token-2022 is backwards-compatible with SPL Token for basic operations.

Open term
ZK Compression

ZKP Syscall (alt_bn128)

The alt_bn128 syscalls are native BPF VM system calls added to the Solana runtime (via SIMD-0041 and related proposals) that expose elliptic curve operations on the BN254 curve (also known as alt_bn128) — specifically point addition, scalar multiplication, and pairing checks — enabling on-chain programs to verify Groth16 zk-SNARK proofs within practical compute unit budgets. Without these syscalls, implementing the pairing-based verification of a Groth16 proof purely in BPF bytecode would require hundreds of millions of compute units, far exceeding the 1.4M per-transaction limit; with the syscalls, a full Groth16 verification costs on the order of 200,000–400,000 compute units. Light Protocol's on-chain verifier and Solana's Token-2022 Confidential Transfers both depend on the alt_bn128 syscalls, making them a critical piece of Solana's ZK infrastructure.

Open term
Commonly confused with

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ZK Compressionlight-token-program

Light Token Program

The ZK Compression program within Light Protocol that handles compressed SPL token operations including minting, transferring, burning, and delegating compressed tokens. It wraps the Light System Program to manage Merkle tree state transitions and validity proofs transparently while exposing an interface similar to standard SPL Token instructions. The Light Token Program enables token operations at a fraction of the cost of regular SPL Token accounts by storing balances as compressed Merkle tree leaves rather than individual on-chain accounts.

Open term
ZK Compressioncompressed-token

Compressed Token

A compressed token is an SPL-compatible fungible or semi-fungible token whose per-account token balances are stored as leaves in a Concurrent Merkle Tree via Light Protocol's Compressed Token Program rather than as individual Token or Token-2022 accounts, reducing the account creation cost from ~0.002 SOL per token account to a negligible fraction of a lamport per leaf. Compressed tokens implement the same mint, transfer, burn, and delegation semantics as standard SPL tokens, but every operation requires a Merkle proof of the source leaf's existence and a validity proof of the state transition; the Compressed Token Program wraps the Light System Program to handle this ZK machinery transparently. This design is particularly valuable for airdrops, gaming economies, and reward systems where millions of user token accounts would otherwise impose prohibitive rent costs on the issuer or recipient.

Open term
ZK Compressionmerkle-proof

Merkle Proof

A Merkle proof is the minimal set of sibling node hashes (the proof path) along the branch from a specific leaf to the tree root, allowing anyone to independently verify that a given leaf is part of a Merkle tree by recomputing the root from the leaf hash and the sibling hashes without needing any other tree data. In Solana's state compression, every compressed account or compressed NFT interaction requires the caller to supply a valid Merkle proof; the on-chain program hashes the proof against the current root stored in the Concurrent Merkle Tree account to confirm inclusion before executing the state change. Proof size scales linearly with tree depth (e.g., a depth-20 tree requires up to 20 sibling hashes, each 32 bytes), so the canopy is used to pre-store upper-level nodes on-chain to reduce the proof data that must be passed in transactions.

Open term
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ZK Compressionelgamal-encryption

ElGamal Encryption

ElGamal encryption is a public-key cryptosystem based on the Diffie-Hellman problem over an elliptic curve group, providing additive homomorphism — meaning the encryption of a sum of values equals the product of their individual ciphertexts — which makes it suitable for confidential token balance accounting where balances can be updated without decrypting them. On Solana, the Token-2022 Confidential Transfers extension uses Twisted ElGamal encryption over the Ristretto255 curve to encrypt token balances in token accounts, so transfers update encrypted balances homomorphically while zero-knowledge range proofs (proving a balance is non-negative and a transfer amount is within bounds) prevent overdrafts without revealing any amounts. Each confidential token account stores a pending encrypted incoming balance and an available encrypted balance, and the account owner uses their ElGamal private key to decrypt and rotate balances via ZK-proof-accompanied instructions.

Open term
ZK Compressionzk-proofs

Zero-Knowledge Proofs (ZKP)

A zero-knowledge proof is a cryptographic protocol by which a prover convinces a verifier that a statement is true — for example, that a state transition is valid — without revealing any information beyond the truth of the statement itself, satisfying the properties of completeness, soundness, and zero-knowledge. In Solana's ecosystem, ZKPs are used by ZK Compression (via Groth16 SNARKs) to prove correct state transitions for compressed accounts without storing full account state on-chain, and by the Token-2022 Confidential Transfers extension (via ElGamal encryption and range proofs) to prove token balances are non-negative without revealing the actual amounts. Solana's BPF VM exposes the alt_bn128 elliptic curve syscall to make on-chain Groth16 proof verification computationally feasible within the 1.4M compute unit budget.

Open term
Token Ecosystemtoken-2022

Token-2022 (Token Extensions)

The next-generation token program (TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb) that extends SPL Token with configurable extensions. Extensions include transfer fees, confidential transfers, transfer hooks, permanent delegate, non-transferable tokens, interest-bearing tokens, metadata, and more. Token-2022 is backwards-compatible with SPL Token for basic operations.

Open term
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ZK Compression

State Compression

State Compression is Solana's technique for storing the cryptographic fingerprint (root hash) of a Merkle tree on-chain while keeping the actual leaf data off-chain in the Solana ledger's account data logs, reducing the cost of storing large datasets by orders of magnitude. A compressed NFT collection of 1 million items costs roughly 50 SOL to mint versus ~12,000 SOL with standard SPL accounts, because only a single Concurrent Merkle Tree account occupies on-chain storage. Any data change requires updating the root hash and supplying a Merkle proof to the on-chain program, which verifies inclusion without reading the full dataset.

Open term
ZK Compression

ZK Compression

ZK Compression, pioneered by Light Protocol, extends Solana's state compression model beyond NFTs to general-purpose compressed accounts by using zero-knowledge proofs (specifically Groth16 SNARKs verified via the alt_bn128 syscall) to prove the validity of state transitions without storing full account state on-chain. Compressed accounts live in on-chain Merkle trees but their data is reconstructed from the Solana ledger by indexers like Photon, enabling developers to build applications that use thousands of accounts at a fraction of the normal rent cost — often 1,000x to 5,000x cheaper than regular accounts. The protocol introduces compressed tokens, compressed PDAs, and a system of nullifiers to prevent double-spends while maintaining Solana's throughput.

Open term
ZK Compression

Compressed Account

A compressed account is a Solana account whose state is stored as a leaf in an on-chain Concurrent Merkle Tree rather than as a dedicated on-chain account, making it 100–1,000x cheaper to create and maintain because no rent-exempt lamport balance is required per account. Compressed accounts are identified by a hash of their data and position in the tree; to interact with one, a client must supply a Merkle proof (or rely on the canopy) showing the leaf is part of the current tree root, which the on-chain program verifies before processing the state change. Light Protocol's compressed account model supports arbitrary data, discriminators, and owner programs, making it a general-purpose replacement for expensive on-chain accounts in high-volume use cases.

Open term
ZK Compression

Concurrent Merkle Tree

A Concurrent Merkle Tree (CMT) is a specialized on-chain Solana data structure that allows multiple state updates to the same Merkle tree within a single block without conflicting, by recording a changelog buffer of recent root transitions that validators use to reconcile parallel proof submissions. A CMT is parameterized by its maximum depth (max_depth, determining tree capacity of 2^max_depth leaves), max_buffer_size (number of concurrent changes the changelog can track, directly controlling how many operations per slot the tree can safely absorb), and an optional canopy_depth. The SPL Account Compression program manages CMTs, and they are the foundational storage primitive for both Metaplex compressed NFTs and Light Protocol compressed accounts.

Open term