| // Copyright 2020 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef THIRD_PARTY_BLINK_PUBLIC_COMMON_PRIVACY_BUDGET_IDENTIFIABILITY_METRICS_H_ |
| #define THIRD_PARTY_BLINK_PUBLIC_COMMON_PRIVACY_BUDGET_IDENTIFIABILITY_METRICS_H_ |
| |
| #include <cstdint> |
| #include <cstring> |
| #include <type_traits> |
| |
| #include "base/containers/span.h" |
| #include "third_party/blink/public/common/common_export.h" |
| |
| namespace blink { |
| |
| // IdentifiabilityDigestOfBytes, which is NOT a cryptographic hash function, |
| // takes a span of bytes as input and calculates a digest that can be used with |
| // identifiability metric reporting functions. |
| // |
| // The returned digest ...: |
| // |
| // * Is Stable: The returned digest will be consistent across different versions |
| // of Chromium. Thus it can be persisted and meaningfully aggregated across |
| // browser versions. |
| // |
| // * Is approximately uniformly distributed when the input is uniformly |
| // distributed. |
| // |
| // * Is NOT optimized for any other distribution of input including narrow |
| // integral ranges. |
| // |
| // * Is NOT collision resistant: Callers should assume that it is easy to come |
| // up with collisions, and to come up with a pre-image given a digest. |
| // |
| // Note: This is NOT a cryptographic hash function. |
| BLINK_COMMON_EXPORT uint64_t |
| IdentifiabilityDigestOfBytes(base::span<const uint8_t> in); |
| |
| // The zero-length digest, i.e. the digest computed for no bytes. |
| static constexpr uint64_t kIdentifiabilityDigestOfNoBytes = |
| UINT64_C(0x9ae16a3b2f90404f); |
| |
| } // namespace blink |
| |
| #endif // THIRD_PARTY_BLINK_PUBLIC_COMMON_PRIVACY_BUDGET_IDENTIFIABILITY_METRICS_H_ |
