> For the complete documentation index, see [llms.txt](https://omnity.gitbook.io/litepaper/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://omnity.gitbook.io/litepaper/ic-enablers/chain-key-cryptography.md).

# Chain-Key Cryptography

IC’s [Chain-Key Cryptography](https://internetcomputer.org/how-it-works/chain-key-technology) enables smart contracts to sign any output data. Omnity leverages Chain-Key to reduce cross-chain costs to the same level as centralized witness-based cross-chain bridges that use TSS (Threshold Signature Scheme) without sacrificing decentralization.

Verifying cross-chain messages on the target chain is usually the most computationally intensive and costly part of a trustless cross-chain process. The Omnity Route smart contract signs cross-chain messages, and the target chain contract authenticates them by checking its signature. No extra gas is needed on EVM target chains for msg sender checking. 

On non-EVM chains, one ECDSA (Elliptic Curve Digital Signature Algorithm) signature verification is still orders of magnitude lower than the most advanced zk-proof verification in terms of gas cost — not to mention on-chain light client verification, which often involves a few dozen or even a few hundred signature checks, plus a Merkle-proof verification.