GenericHash

public class GenericHash

This class can be used to generate hash arbitrary data. Keyed hashing is supported.

Warning

Do not use this for hashing passwords, as there is no protection against fast brute-force attacks. Use HashedPassword for that purpose.

Examples

Public Hashing

let data = "Hello, World!".utf8Bytes
let hash = GenericHash(bytes: data)

Private Hashing with Persisted Keys

// Create a persona
let alice = Persona(uniqueName: "Alice")

// Generate a personalized hash for that persona
let data = "Hello, World!".utf8Bytes
let hash = GenericHash(bytes: data, for: alice)

// Forget the persona and remove all related Keychain entries
try! Persona.forget(alice)

Key
This class represents a key that can be used for hashing.
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Declaration
Swift

public class Key : KeyMaterial
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MinimumSizeInBytes
The minimum size of the hash in bytes.
Declaration
Swift

public static let MinimumSizeInBytes: UInt32
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MaximumSizeInBytes
The maximum size of the hash in bytes.
Declaration
Swift

public static let MaximumSizeInBytes: UInt32
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DefaultSizeInBytes
The default size of the hash in bytes.
Declaration
Swift

public static let DefaultSizeInBytes: UInt32
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bytes
The hash.
Declaration
Swift

private let bytes: Bytes
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                    init(bytes:outputSizeInBytes:with:)

Hash an arbitrary value.

The size needs to be within the given bounds: MinimumSizeInBytes ≤ outputSizeInBytes ≤ MaximumSizeInBytes.

Warning

Do not use this for hashing passwords, as there is no protection against fast brute-force attacks. Use HashedPassword for that purpose.

This is not protected against rainbow attacks if you do not provide a key.

Declaration

Swift

public init?(bytes: Bytes, outputSizeInBytes: UInt32 = GenericHash.DefaultSizeInBytes, with key: Key? = nil)

Parameters

`bytes`	The value that should be hashed.
`outputSizeInBytes`	The size of the hash in bytes.
`key`	A key/salt used to prevent the hash from being guessed.

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                    init(bytes:for:outputSizeInBytes:)

Hash an arbitrary value for a given persona.

The size needs to be within the given bounds: MinimumSizeInBytes ≤ outputSizeInBytes ≤ MaximumSizeInBytes.

This is protected against rainbow attacks.

Warning

Do not use this for hashing passwords, as there is no protection against fast brute-force attacks. Use HashedPassword for that purpose.

Declaration

Swift

public convenience init?(bytes: Bytes, for persona: Persona, outputSizeInBytes: UInt32 = GenericHash.DefaultSizeInBytes)

Parameters

`bytes`	The value that should be hashed.
`persona`	The persona to which the hash is tied to.
`outputSizeInBytes`	The size of the hash in bytes.

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                    init(hex:)

Restore a hash from a hex string.

Declaration

Swift

public init?(hex: String)

Parameters

hex

The hash as a hex encoded string.

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sizeInBytes
The size of the hash in bytes.
Declaration
Swift

public var sizeInBytes: UInt32 { get }
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hexlify
A hex encoded string representing the hash.
Declaration
Swift

public var hexlify: String { get }
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                    ==(_:_:)

Compares two hashes in constant time.

Note

An attacker might be able to identify the length of the hash with a timing attack. But as the size bounds for hashes are publicly known and the minimum size is sufficiently long, this should not be a cause for problems.

Declaration

Swift

public static func == (lhs: GenericHash, rhs: GenericHash) -> Bool

Parameters

`lhs`	A hash.
`rhs`	Another hash.

Return Value

true if both hashes are equal, false else.

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hashValue
The hash value according to the Hashable protocol.

Warning
This is not the value of the generic hash but a value used for improving performance of data structures.
Declaration
Swift

public var hashValue: Int { get }
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