Sensitivity, Laplace noise and composition
Research context
research method · established · As of 2026-10-10
For a vector query with global L1 sensitivity Delta-1, adding independent Laplace noise of scale Delta-1/epsilon to each coordinate gives epsilon-DP under the chosen adjacency.
Key knowledge
For a vector query with global L1 sensitivity Delta-1, adding independent Laplace noise of scale Delta-1/epsilon to each coordinate gives epsilon-DP under the chosen adjacency. Postprocessing without new private-data access preserves that guarantee. Adaptive composition adds epsilon values and delta values in the basic bound; repeated releases consume privacy budget even if each release looks noisy. Utility depends on sensitivity, dimensions and the task's tolerated error.
Values and equations
Delta_1=sup_(D~D') ||f(D)−f(D')||_1; noise_j~Laplace(Delta_1/epsilon)
- f
- Vector-valued query
- Delta_1
- Finite global L1 sensitivity in query-output units
- epsilon
- Positive privacy budget
Conditions and scope
- epsilon>0 for the Laplace construction; global sensitivity is a finite supremum over every allowed neighboring pair. If sensitivity is zero, a constant query requires no added noise; an infinite sensitivity does not give this finite-noise construction.
- A data-dependent choice of query or noise scale must itself be covered by the mechanism's privacy accounting.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Author checked this English statement, displayed equation where present and stated hypotheses against these source locations: Definition 2.4, postprocessing, composition, Laplace mechanism and advanced composition Theorem 3.20. The check is bounded to the recorded claims; no complete proof reconstruction, software proof replay or universal literature completeness is claimed.
2026-10-10 · Author source-body/statement/equation/domain check, with graph associations scoped individually. Separate independent content/source/inventory review is required before branch closure.
Entry details
Permanent link to this entry ↗- Record identity
- research-info-private-mechanism-composition
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference