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.

    See more

    Declaration

    Swift

    public class Key : KeyMaterial
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  • The minimum size of the hash in bytes.

    Declaration

    Swift

    public static let MinimumSizeInBytes: UInt32
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  • The maximum size of the hash in bytes.

    Declaration

    Swift

    public static let MaximumSizeInBytes: UInt32
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  • The default size of the hash in bytes.

    Declaration

    Swift

    public static let DefaultSizeInBytes: UInt32
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  • 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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  • 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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  • 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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  • The size of the hash in bytes.

    Declaration

    Swift

    public var sizeInBytes: UInt32 { get }
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  • 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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  • 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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