---
name: "Mail::DKIM::ARC::MessageSignature"
section: "3pm"
platform: "linux"
package: "perl-mail-dkim"
version: "1.20240923-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/Mail::DKIM::ARC::MessageSignature"
---

# Mail::DKIM::ARC::MessageSignature(3pm)

Subclass of Mail::DKIM::Signature which represents a ARC-Message-Signature header

## NAME

Mail::DKIM::ARC::MessageSignature - Subclass of Mail::DKIM::Signature which represents a ARC-Message-Signature header

## VERSION

version 1.20240923

## CONSTRUCTORS

### new() - create a new signature from parameters

```
  my $signature = Mail::DKIM::ARC::MessageSignature->new(
                      [ Algorithm => 'rsa-sha256', ]
                      [ Signature => $base64, ]
                      [ Method => 'relaxed', ]
                      [ Domain => 'example.org', ]
                      [ Instance => 1, ]
                      [ Headers => 'from:subject:date:message-id', ]
                      [ Query => 'dns', ]
                      [ Selector => 'alpha', ]
                      [ Timestamp => time(), ]
                      [ Expiration => time() + 86400, ]
                  );
```

The only differences between this module and Mail::DKIM::Signature are the header name, and that 'instance' is an integer rather than a base64 encoded value.

### instance() - get or set the signing instance (i=) field

```
  my $i = $signature->instance;
```

Instances must be integers less than 1024 according to the spec.

NOTE: the i= field is "Identity" in DKIM and is a base64 value, but in ARC it is "Instance" and an integer.  The parsing routine does not check that the i= value is a number.

## SEE ALSO

Mail::DKIM::Signature for DKIM-Signature headers

## AUTHORS

- •

  Jason Long \<jason@long.name\>

- •

  Marc Bradshaw \<marc@marcbradshaw.net\>

- •

  Bron Gondwana \<brong@fastmailteam.com\> (ARC)

## THANKS

Work on ensuring that this module passes the ARC test suite was generously sponsored by Valimail (https://www.valimail.com/)

## COPYRIGHT AND LICENSE

- •

  Copyright (C) 2013 by Messiah College

- •

  Copyright (C) 2010 by Jason Long

- •

  Copyright (C) 2017 by Standcore LLC

- •

  Copyright (C) 2020 by FastMail Pty Ltd

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.6 or, at your option, any later version of Perl 5 you may have available.