TAtlasBytes

ToHex method

class function ToHex(const Data: TBytes): string; static;

Returns lower-case hexadecimal, two digits per byte. An empty array gives an empty string.

HexText := TAtlasBytes.ToHex(TBytes.Create($00, $AB, $FF));  // 00abff

FromHex method

class function FromHex(const Text: string): TBytes; static;

Parses hexadecimal digits in either case. Raises EAtlasCryptoError for an odd number of digits or any other character, including a 0x prefix or spaces.

Data := TAtlasBytes.FromHex('00ABff');

ToBase64Url method

class function ToBase64Url(const Data: TBytes): string; static;

Returns base64 in the URL-safe alphabet (- and _ instead of + and /), without = padding and without line breaks, however long the data.

Text := TAtlasBytes.ToBase64Url(TAtlasRandom.Bytes(32));  // 43 characters

FromBase64Url method

class function FromBase64Url(const Text: string): TBytes; static;

Parses text made by ToBase64Url. Raises EAtlasCryptoError (The text is not URL-safe base64) for any character outside A-Z, a-z, 0-9, - and _ (so padding, white space and the standard + and / are refused), and for an impossible length.

Data := TAtlasBytes.FromBase64Url(Text);

OfString method

class function OfString(const Text: string): TBytes; static;

Returns the UTF-8 encoding of Text, the form every text-taking function in Atlas Crypto uses.

Data := TAtlasBytes.OfString('grüße');  // 7 bytes

Concat method

class function Concat(const Parts: array of TBytes): TBytes; static;

Joins the parts in order into a new array. Empty parts are skipped; no parts give an empty array.

Data := TAtlasBytes.Concat([TAtlasBytes.OfString('v1:'), Key]);

ConstantTimeEquals method

class function ConstantTimeEquals(const A, B: TBytes): Boolean; static;

True when both arrays have the same length and content. For equal lengths the time taken depends only on the length, never on where the first difference is, so a comparison cannot leak a secret byte by byte. Arrays of different lengths return False at once. Two empty arrays are equal.

Valid := TAtlasBytes.ConstantTimeEquals(Tag, TAtlasHash.Hmac(hkSHA256, Key, Data));

Wipe method

class procedure Wipe(var Data: TBytes); static;

Overwrites the content with zeros, then sets Data to an empty array. Safe to call on an empty array.

TAtlasBytes.Wipe(Key);

Encode, compare and wipe

Prints 00abff, AKv_ and TRUE, then 0 after the wipe.

uses System.SysUtils, Atlas.Crypto;

procedure ByteHelpers;
var
  Secret: TBytes;
begin
  Secret := TBytes.Create($00, $AB, $FF);
  WriteLn(TAtlasBytes.ToHex(Secret));
  WriteLn(TAtlasBytes.ToBase64Url(Secret));
  WriteLn(TAtlasBytes.ConstantTimeEquals(TAtlasBytes.FromBase64Url('AKv_'), TAtlasBytes.FromHex('00ABFF')));
  TAtlasBytes.Wipe(Secret);
  WriteLn(Length(Secret));
end;