RFC 8463 - A New Cryptographic Signature Method for DomainKeys Identified Mail (DKIM)

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<span class="ms-sm-3 badge rounded-pill badge-ps"> Proposed Standard </span> </a> <button class="navbar-toggler p-1" type="button" data-bs-toggle="collapse" data-bs-target="#docinfo-collapse" aria-controls="docinfo-collapse" aria-expanded="false" aria-label="Show document information"> <span class="navbar-toggler-icon small"></span> </button> <div class="navbar-nav navbar-nav-scroll overscroll-none collapse pt-1" id="docinfo-collapse"> <div class="bg-light-subtle p-0"> <table class="table table-sm table-borderless small"> <tbody class="meta align-top"> <tr> <th scope="row"></th> <th scope="row">Title</th> <td class="edit"></td> <td>A New Cryptographic Signature Method for DomainKeys Identified Mail (DKIM)</td> </tr> </tbody> <tbody class="meta align-top "> <tr> <th scope="row">Document</th> <th scope="row">Document type</th> <td class="edit"></td> <td> <span class="text-success">RFC - Proposed Standard </span> <br>September 2018 <br> <a class="btn btn-sm btn-warning" title="Click to report an error in the document." href="https://www.rfc-editor.org/errata.php#reportnew" target="_blank"> Report errata </a> <div>Updates <a href="/doc/html/rfc6376" title="DomainKeys Identified Mail (DKIM) Signatures">RFC 6376</a></div> <div> Was <a href="/doc/draft-ietf-dcrup-dkim-crypto/14/">draft-ietf-dcrup-dkim-crypto</a> (<a href="/wg/dcrup/about/">dcrup WG</a>) </div> </td> </tr> <tr> <td></td> <th scope="row">Select version</th> <td class="edit"></td> <td> <ul class="revision-list pagination pagination-sm text-center flex-wrap my-0"> <li class="page-item"> <a class="page-link" href="/doc/html/draft-ietf-dcrup-dkim-crypto-00" rel="nofollow"> 00 </a> </li> <li class="page-item"> <a class="page-link" href="/doc/html/draft-ietf-dcrup-dkim-crypto-01" rel="nofollow"> 01 </a> </li> <li class="page-item"> <a class="page-link" href="/doc/html/draft-ietf-dcrup-dkim-crypto-02" rel="nofollow"> 02 </a> </li> <li class="page-item"> <a class="page-link" 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Levine" href="/person/ietf@johnlevine.com" >John R. Levine</a> <a href="mailto:ietf%40johnlevine.com" aria-label="Compose email to ietf@johnlevine.com" title="Compose email to ietf@johnlevine.com"> <i class="bi bi-envelope"></i></a></span> <br> <a class="btn btn-primary btn-sm mt-1" href="mailto:rfc8463@ietf.org?subject=rfc8463" title="Send email to the document authors">Email authors</a> </td> </tr> <tr> <td></td> <th scope="row"> RFC stream </th> <td class="edit"> </td> <td > <img alt="IETF Logo" class="d-lm-none w-25 mt-1" src="https://static.ietf.org/dt/12.28.2/ietf/images/ietf-logo-nor-white.svg" > <img alt="IETF Logo" class="d-dm-none w-25 mt-1" src="https://static.ietf.org/dt/12.28.2/ietf/images/ietf-logo-nor.svg" > </td> </tr> <tr> <td></td> <th scope="row"> Other formats </th> <td class="edit"> </td> <td> <div class="buttonlist"> <a class="btn btn-primary btn-sm" target="_blank" href="https://www.rfc-editor.org/rfc/rfc8463.txt"> <i class="bi bi-file-text"></i> txt </a> <a class="btn btn-primary btn-sm" target="_blank" href="https://www.rfc-editor.org/rfc/rfc8463.html"> <i class="bi bi-file-code"></i> html </a> <a class="btn btn-primary btn-sm" download="rfc8463.pdf" target="_blank" href="https://www.rfc-editor.org/rfc/pdfrfc/rfc8463.txt.pdf"> <i class="bi bi-file-pdf"></i> pdf </a> <a class="btn btn-primary btn-sm" target="_blank" href="/doc/rfc8463/bibtex/"> <i class="bi bi-file-ruled"></i> bibtex </a> </div> </td> </tr> <tr> <td> </td> <th scope="row"> Additional resources </th> <td class="edit"> </td> <td> <a href="https://mailarchive.ietf.org/arch/browse/dcrup/?q=rfc8463 OR %22draft-ietf-dcrup-dkim-crypto%22"> Mailing list discussion </a> </td> </tr> </tbody> <tr> <th scope="row"></th> <th scope="row"></th> <td class="edit"></td> <td> <a class="btn btn-sm btn-warning mb-3" target="_blank" href="https://github.com/ietf-tools/datatracker/issues/new/choose"> Report a bug <i class="bi bi-bug"></i> </a> </td> </tr> </table> </div> </div> </nav> <div class="row g-0"> <div class="col-md-9 d-flex justify-content-center lh-sm" data-bs-spy="scroll" data-bs-target="#toc-nav" data-bs-smooth-scroll="true" tabindex="0" id="content"> <div class="rfcmarkup"> <br class="noprint">  <div class="rfcmarkup"><pre>Internet Engineering Task Force (IETF) J. Levine Request for Comments: 8463 Taughannock Networks Updates: <a href="/doc/html/rfc6376">6376</a> September 2018 Category: Standards Track ISSN: 2070-1721 <span class="h1">A New Cryptographic Signature Method for</span> <span class="h1">DomainKeys Identified Mail (DKIM)</span> Abstract This document adds a new signing algorithm, Ed25519-SHA256, to "DomainKeys Identified Mail (DKIM) Signatures" (<a href="/doc/html/rfc6376">RFC 6376</a>). DKIM verifiers are required to implement this algorithm. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in <a href="/doc/html/rfc7841#section-2">Section 2 of RFC 7841</a>. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at <a href="https://www.rfc-editor.org/info/rfc8463">https://www.rfc-editor.org/info/rfc8463</a>. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to <a href="/doc/html/bcp78">BCP 78</a> and the IETF Trust's Legal Provisions Relating to IETF Documents (<a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a>) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. <span class="grey">Levine Standards Track [Page 1]</span></pre> <hr class='noprint'/><pre class='newpage'><span id="page-2" ></span> <span class="grey"><a href="/doc/html/rfc8463">RFC 8463</a> DKIM Crypto Update September 2018</span> Table of Contents <a href="#section-1">1</a>. Introduction . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-2">2</a> <a href="#section-2">2</a>. Conventions Used in This Document . . . . . . . . . . . . . . <a href="#page-2">2</a> <a href="#section-3">3</a>. Ed25519-SHA256 Signing Algorithm . . . . . . . . . . . . . . <a href="#page-3">3</a> <a href="#section-4">4</a>. Signature and Key Syntax . . . . . . . . . . . . . . . . . . <a href="#page-3">3</a> <a href="#section-4.1">4.1</a>. Signature Syntax . . . . . . . . . . . . . . . . . . . . <a href="#page-3">3</a> <a href="#section-4.2">4.2</a>. Key Syntax . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-3">3</a> <a href="#section-5">5</a>. Choice and Strength of Keys and Algorithms . . . . . . . . . <a href="#page-4">4</a> <a href="#section-6">6</a>. Transition Considerations . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a> <a href="#section-7">7</a>. Security Considerations . . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a> <a href="#section-8">8</a>. IANA Considerations . . . . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a> <a href="#section-8.1">8.1</a>. "DKIM Key Type" Registry . . . . . . . . . . . . . . . . <a href="#page-4">4</a> <a href="#section-9">9</a>. References . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-5">5</a> <a href="#section-9.1">9.1</a>. Normative References . . . . . . . . . . . . . . . . . . <a href="#page-5">5</a> <a href="#section-9.2">9.2</a>. Informative References . . . . . . . . . . . . . . . . . <a href="#page-5">5</a> <a href="#appendix-A">Appendix A</a>. Example of a Signed Message . . . . . . . . . . . . <a href="#page-6">6</a> <a href="#appendix-A.1">A.1</a>. Secret Keys . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-6">6</a> <a href="#appendix-A.2">A.2</a>. Public Key DNS Records . . . . . . . . . . . . . . . . . <a href="#page-6">6</a> <a href="#appendix-A.3">A.3</a>. Signed Message . . . . . . . . . . . . . . . . . . . . . <a href="#page-7">7</a> Author's Address . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-7">7</a> <span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span> DKIM [<a href="/doc/html/rfc6376" title=""DomainKeys Identified Mail (DKIM) Signatures"">RFC6376</a>] signs email messages by creating hashes of selected message header fields and body and signing the header hash with a digital signature. Message recipients fetch the signature verification key from the DNS. The defining documents specify a single signing algorithm, RSA [<a href="/doc/html/rfc3447" title=""Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1"">RFC3447</a>] (which has since been obsoleted by [<a href="/doc/html/rfc8017" title=""PKCS #1: RSA Cryptography Specifications Version 2.2"">RFC8017</a>]). This document adds a new, stronger signing algorithm, Edwards-Curve Digital Signature Algorithm, using the Curve25519 curve (Ed25519), which has much shorter keys than RSA for similar levels of security. <span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Conventions Used in This Document</span> The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in <a href="/doc/html/bcp14">BCP 14</a> [<a href="/doc/html/rfc2119" title=""Key words for use in RFCs to Indicate Requirement Levels"">RFC2119</a>] [<a href="/doc/html/rfc8174" title=""Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"">RFC8174</a>] when, and only when, they appear in all capitals, as shown here. Syntax descriptions use Augmented BNF (ABNF) [<a href="/doc/html/rfc5234" title=""Augmented BNF for Syntax Specifications: ABNF"">RFC5234</a>]. The ABNF tokens sig-a-tag-k and key-k-tag-type are imported from [<a href="/doc/html/rfc6376" title=""DomainKeys Identified Mail (DKIM) Signatures"">RFC6376</a>]. <span class="grey">Levine Standards Track [Page 2]</span></pre> <hr class='noprint'/><pre class='newpage'><span id="page-3" ></span> <span class="grey"><a href="/doc/html/rfc8463">RFC 8463</a> DKIM Crypto Update September 2018</span> <span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Ed25519-SHA256 Signing Algorithm</span> The Ed25519-SHA256 signing algorithm computes a message hash as defined in <a href="/doc/html/rfc6376#section-3">Section 3 of [RFC6376]</a> using SHA-256 [<a href="#ref-FIPS-180-4-2015">FIPS-180-4-2015</a>] as the hash-alg. It signs the hash with the PureEdDSA variant Ed25519, as defined in <a href="/doc/html/rfc8032#section-5.1">RFC 8032, Section 5.1</a> [<a href="/doc/html/rfc8032" title=""Edwards-Curve Digital Signature Algorithm (EdDSA)"">RFC8032</a>]. Example keys and signatures in <a href="#appendix-A">Appendix A</a> are based on the test vectors in <a href="/doc/html/rfc8032#section-7.1">RFC 8032, Section 7.1</a> [<a href="/doc/html/rfc8032" title=""Edwards-Curve Digital Signature Algorithm (EdDSA)"">RFC8032</a>]. The DNS record for the verification public key has a "k=ed25519" tag to indicate that the key is an Ed25519 rather than an RSA key. This is an additional DKIM signature algorithm added to <a href="/doc/html/rfc6376#section-3.3">Section 3.3 of [RFC6376]</a> as envisioned in <a href="#section-3.3.4">Section 3.3.4</a> of that document. Note: since Ed25519 public keys are 256 bits long, the base64-encoded key is only 44 octets, so DNS key record data will generally fit in a single 255-byte TXT string and work even with DNS provisioning software that doesn't handle multistring TXT records. <span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Signature and Key Syntax</span> The syntax of DKIM signatures and DKIM keys are updated as follows. <span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>. Signature Syntax</span> The syntax of DKIM algorithm tags in <a href="/doc/html/rfc6376#section-3.5">Section 3.5 of [RFC6376]</a> is updated by adding this rule to the existing rule for sig-a-tag-k: ABNF: sig-a-tag-k =/ "ed25519" <span class="h3"><a class="selflink" id="section-4.2" href="#section-4.2">4.2</a>. Key Syntax</span> The syntax of DKIM key tags in <a href="/doc/html/rfc6376#section-3.6.1">Section 3.6.1 of [RFC6376]</a> is updated by adding this rule to the existing rule for key-k-tag-type: ABNF: key-k-tag-type =/ "ed25519" The p= value in the key record is the Ed25519 public key encoded in base64. Since the key is 256 bits long, the base64 text is 44 octets long. See <a href="#appendix-A.2">Appendix A.2</a> for a sample key record using the public key in <a href="/doc/html/rfc8032#section-7.1">[RFC8032], Section 7.1</a>, Test 1. <span class="grey">Levine Standards Track [Page 3]</span></pre> <hr class='noprint'/><pre class='newpage'><span id="page-4" ></span> <span class="grey"><a href="/doc/html/rfc8463">RFC 8463</a> DKIM Crypto Update September 2018</span> <span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Choice and Strength of Keys and Algorithms</span> <a href="/doc/html/rfc6376#section-3.3">Section 3.3 of [RFC6376]</a> describes DKIM's hash and signature algorithms. It is updated as follows: Signers SHOULD implement and verifiers MUST implement the Ed25519-SHA256 algorithm. <span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Transition Considerations</span> For backward compatibility, signers can add multiple signatures that use old and new signing algorithms. Since there can only be a single key record in the DNS for each selector, the signatures have to use different selectors, although they can use the same d= and i= identifiers. The example message in <a href="#appendix-A">Appendix A</a> has two signatures with the same d= and i= identifiers but different a= algorithms and s= selectors. <span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. Security Considerations</span> All of the security advice in [<a href="/doc/html/rfc6376" title=""DomainKeys Identified Mail (DKIM) Signatures"">RFC6376</a>] continues to apply, except that the security advice about Ed25519 in <a href="/doc/html/rfc8032#section-8">Section 8 of [RFC8032]</a> supplants the advice about RSA threats. <span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. IANA Considerations</span> IANA has updated a registry as follows. <span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>. "DKIM Key Type" Registry</span> The following value has been added to the "DKIM Key Type" registry: +---------+-----------+--------+ | TYPE | REFERENCE | STATUS | +---------+-----------+--------+ | ed25519 | [<a href="/doc/html/rfc8032" title=""Edwards-Curve Digital Signature Algorithm (EdDSA)"">RFC8032</a>] | active | +---------+-----------+--------+ Table 1: Value Added to the "DKIM Key Type" Registry <span class="grey">Levine Standards Track [Page 4]</span></pre> <hr class='noprint'/><pre class='newpage'><span id="page-5" ></span> <span class="grey"><a href="/doc/html/rfc8463">RFC 8463</a> DKIM Crypto Update September 2018</span> <span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>. References</span> <span class="h3"><a class="selflink" id="section-9.1" href="#section-9.1">9.1</a>. Normative References</span> [<a id="ref-FIPS-180-4-2015">FIPS-180-4-2015</a>] National Institute of Standards and Technology, "Secure Hash Standard (SHS)", FIPS PUB 180-4, DOI 10.6028/NIST.FIPS.180-4, August 2015, <<a href="http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf">http://nvlpubs.nist.gov/nistpubs/FIPS/</a> <a href="http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf">NIST.FIPS.180-4.pdf</a>>. [<a id="ref-RFC2119">RFC2119</a>] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", <a href="/doc/html/bcp14">BCP 14</a>, <a href="/doc/html/rfc2119">RFC 2119</a>, DOI 10.17487/RFC2119, March 1997, <<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>>. [<a id="ref-RFC5234">RFC5234</a>] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, <a href="/doc/html/rfc5234">RFC 5234</a>, DOI 10.17487/RFC5234, January 2008, <<a href="https://www.rfc-editor.org/info/rfc5234">https://www.rfc-editor.org/info/rfc5234</a>>. [<a id="ref-RFC6376">RFC6376</a>] Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed., "DomainKeys Identified Mail (DKIM) Signatures", STD 76, <a href="/doc/html/rfc6376">RFC 6376</a>, DOI 10.17487/RFC6376, September 2011, <<a href="https://www.rfc-editor.org/info/rfc6376">https://www.rfc-editor.org/info/rfc6376</a>>. [<a id="ref-RFC8017">RFC8017</a>] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch, "PKCS #1: RSA Cryptography Specifications Version 2.2", <a href="/doc/html/rfc8017">RFC 8017</a>, DOI 10.17487/RFC8017, November 2016, <<a href="https://www.rfc-editor.org/info/rfc8017">https://www.rfc-editor.org/info/rfc8017</a>>. [<a id="ref-RFC8032">RFC8032</a>] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital Signature Algorithm (EdDSA)", <a href="/doc/html/rfc8032">RFC 8032</a>, DOI 10.17487/RFC8032, January 2017, <<a href="https://www.rfc-editor.org/info/rfc8032">https://www.rfc-editor.org/info/rfc8032</a>>. [<a id="ref-RFC8174">RFC8174</a>] Leiba, B., "Ambiguity of Uppercase vs Lowercase in <a href="/doc/html/rfc2119">RFC</a> <a href="/doc/html/rfc2119">2119</a> Key Words", <a href="/doc/html/bcp14">BCP 14</a>, <a href="/doc/html/rfc8174">RFC 8174</a>, DOI 10.17487/RFC8174, May 2017, <<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>>. <span class="h3"><a class="selflink" id="section-9.2" href="#section-9.2">9.2</a>. Informative References</span> [<a id="ref-RFC3447">RFC3447</a>] Jonsson, J. and B. Kaliski, "Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1", <a href="/doc/html/rfc3447">RFC 3447</a>, DOI 10.17487/RFC3447, February 2003, <<a href="https://www.rfc-editor.org/info/rfc3447">https://www.rfc-editor.org/info/rfc3447</a>>. <span class="grey">Levine Standards Track [Page 5]</span></pre> <hr class='noprint'/><pre class='newpage'><span id="page-6" ></span> <span class="grey"><a href="/doc/html/rfc8463">RFC 8463</a> DKIM Crypto Update September 2018</span> <span class="h2"><a class="selflink" id="appendix-A" href="#appendix-A">Appendix A</a>. Example of a Signed Message</span> This is a small message with both RSA-SHA256 and Ed25519-SHA256 DKIM signatures. The signatures are independent of each other, so either signature would be valid if the other were not present. <span class="h3"><a class="selflink" id="appendix-A.1" href="#appendix-A.1">A.1</a>. Secret Keys</span> Ed25519 secret key in base64. This is the secret key from <a href="/doc/html/rfc8032#section-7.1">[RFC8032], Section 7.1</a>, Test 1, converted from hex to base64. nWGxne/9WmC6hEr0kuwsxERJxWl7MmkZcDusAxyuf2A= RSA secret key in PEM format. -----BEGIN RSA PRIVATE KEY----- MIICXQIBAAKBgQDkHlOQoBTzWRiGs5V6NpP3idY6Wk08a5qhdR6wy5bdOKb2jLQi Y/J16JYi0Qvx/byYzCNb3W91y3FutACDfzwQ/BC/e/8uBsCR+yz1Lxj+PL6lHvqM KrM3rG4hstT5QjvHO9PzoxZyVYLzBfO2EeC3Ip3G+2kryOTIKT+l/K4w3QIDAQAB AoGAH0cxOhFZDgzXWhDhnAJDw5s4roOXN4OhjiXa8W7Y3rhX3FJqmJSPuC8N9vQm 6SVbaLAE4SG5mLMueHlh4KXffEpuLEiNp9Ss3O4YfLiQpbRqE7Tm5SxKjvvQoZZe zHorimOaChRL2it47iuWxzxSiRMv4c+j70GiWdxXnxe4UoECQQDzJB/0U58W7RZy 6enGVj2kWF732CoWFZWzi1FicudrBFoy63QwcowpoCazKtvZGMNlPWnC7x/6o8Gc uSe0ga2xAkEA8C7PipPm1/1fTRQvj1o/dDmZp243044ZNyxjg+/OPN0oWCbXIGxy WvmZbXriOWoSALJTjExEgraHEgnXssuk7QJBALl5ICsYMu6hMxO73gnfNayNgPxd WFV6Z7ULnKyV7HSVYF0hgYOHjeYe9gaMtiJYoo0zGN+L3AAtNP9huqkWlzECQE1a licIeVlo1e+qJ6Mgqr0Q7Aa7falZ448ccbSFYEPD6oFxiOl9Y9se9iYHZKKfIcst o7DUw1/hz2Ck4N5JrgUCQQCyKveNvjzkkd8HjYs0SwM0fPjK16//5qDZ2UiDGnOe uEzxBDAr518Z8VFbR41in3W4Y3yCDgQlLlcETrS+zYcL -----END RSA PRIVATE KEY----- <span class="h3"><a class="selflink" id="appendix-A.2" href="#appendix-A.2">A.2</a>. Public Key DNS Records</span> The public key p= value in the first record is the public key from <a href="/doc/html/rfc8032#section-7.1">[RFC8032], Section 7.1</a>, Test 1, converted from hex to base64. brisbane._domainkey.football.example.com. IN TXT ( "v=DKIM1; k=ed25519; p=11qYAYKxCrfVS/7TyWQHOg7hcvPapiMlrwIaaPcHURo=") test._domainkey.football.example.com. IN TXT ( "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDkHlOQoBTzWR" "iGs5V6NpP3idY6Wk08a5qhdR6wy5bdOKb2jLQiY/J16JYi0Qvx/byYzCNb3W91y3FutAC" "DfzwQ/BC/e/8uBsCR+yz1Lxj+PL6lHvqMKrM3rG4hstT5QjvHO9PzoxZyVYLzBfO2EeC3" "Ip3G+2kryOTIKT+l/K4w3QIDAQAB") <span class="grey">Levine Standards Track [Page 6]</span></pre> <hr class='noprint'/><pre class='newpage'><span id="page-7" ></span> <span class="grey"><a href="/doc/html/rfc8463">RFC 8463</a> DKIM Crypto Update September 2018</span> <span class="h3"><a class="selflink" id="appendix-A.3" href="#appendix-A.3">A.3</a>. Signed Message</span> The text in each line of the message starts at the first position except for the continuation lines on the DKIM-Signature header fields, which start with a single space. A blank line follows the "Joe." line. DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=football.example.com; i=@football.example.com; q=dns/txt; s=brisbane; t=1528637909; h=from : to : subject : date : message-id : from : subject : date; bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=; b=/gCrinpcQOoIfuHNQIbq4pgh9kyIK3AQUdt9OdqQehSwhEIug4D11Bus Fa3bT3FY5OsU7ZbnKELq+eXdp1Q1Dw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=football.example.com; i=@football.example.com; q=dns/txt; s=test; t=1528637909; h=from : to : subject : date : message-id : from : subject : date; bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=; b=F45dVWDfMbQDGHJFlXUNB2HKfbCeLRyhDXgFpEL8GwpsRe0IeIixNTe3 DhCVlUrSjV4BwcVcOF6+FF3Zo9Rpo1tFOeS9mPYQTnGdaSGsgeefOsk2Jz dA+L10TeYt9BgDfQNZtKdN1WO//KgIqXP7OdEFE4LjFYNcUxZQ4FADY+8= From: Joe SixPack <joe@football.example.com> To: Suzie Q <suzie@shopping.example.net> Subject: Is dinner ready? Date: Fri, 11 Jul 2003 21:00:37 -0700 (PDT) Message-ID: <20030712040037.46341.5F8J@football.example.com> Hi. We lost the game. Are you hungry yet? Joe. Author's Address John Levine Taughannock Networks PO Box 727 Trumansburg, NY 14886 United States of America Phone: +883.5100.01196712 Email: standards@taugh.com Levine Standards Track [Page 7] </pre></div> </div> </div> <div class="d-print-none col-md-3 bg-light-subtle collapse show" id="sidebar"> <div class="position-fixed border-start sidebar overflow-scroll overscroll-none no-scrollbar"> <div class="d-flex flex-column vh-100 pt-2 pt-lg-3 ps-3 pl-md-2 pl-lg-3"> <div> <a class="btn btn-primary btn-sm" href="/doc/rfc8463/">Datatracker</a> <p class="fw-bold pt-2"> RFC 8463 <br> <span class="text-success">RFC - Proposed Standard </span> </p> </div> <ul class="nav nav-tabs nav-fill small me-2" role="tablist"> <li class="nav-item" role="presentation" title="Document information"> <button class="nav-link px-2" id="docinfo-tab" data-bs-toggle="tab" data-bs-target="#docinfo-tab-pane" type="button" role="tab" aria-controls="docinfo-tab-pane" aria-selected="true"> <i class="bi 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<option value="draft-ietf-dcrup-dkim-crypto-06"> draft-ietf-dcrup-dkim-crypto-06 </option> <option value="draft-ietf-dcrup-dkim-crypto-05"> draft-ietf-dcrup-dkim-crypto-05 </option> <option value="draft-ietf-dcrup-dkim-crypto-04"> draft-ietf-dcrup-dkim-crypto-04 </option> <option value="draft-ietf-dcrup-dkim-crypto-03"> draft-ietf-dcrup-dkim-crypto-03 </option> <option value="draft-ietf-dcrup-dkim-crypto-02"> draft-ietf-dcrup-dkim-crypto-02 </option> <option value="draft-ietf-dcrup-dkim-crypto-01"> draft-ietf-dcrup-dkim-crypto-01 </option> <option value="draft-ietf-dcrup-dkim-crypto-00"> draft-ietf-dcrup-dkim-crypto-00 </option> </select> <select class="form-select form-select-sm mb-1 select2-field" data-max-entries="1" data-width="resolve" data-allow-clear="false" data-minimum-input-length="0" aria-label="To revision" name="url2"> <option value="rfc8463" selected> RFC 8463 </option> <option value="draft-ietf-dcrup-dkim-crypto-14"> draft-ietf-dcrup-dkim-crypto-14 </option> <option value="draft-ietf-dcrup-dkim-crypto-13"> draft-ietf-dcrup-dkim-crypto-13 </option> <option value="draft-ietf-dcrup-dkim-crypto-12"> draft-ietf-dcrup-dkim-crypto-12 </option> <option value="draft-ietf-dcrup-dkim-crypto-11"> draft-ietf-dcrup-dkim-crypto-11 </option> <option value="draft-ietf-dcrup-dkim-crypto-10"> draft-ietf-dcrup-dkim-crypto-10 </option> <option value="draft-ietf-dcrup-dkim-crypto-09"> draft-ietf-dcrup-dkim-crypto-09 </option> <option value="draft-ietf-dcrup-dkim-crypto-08"> draft-ietf-dcrup-dkim-crypto-08 </option> <option value="draft-ietf-dcrup-dkim-crypto-07"> draft-ietf-dcrup-dkim-crypto-07 </option> <option value="draft-ietf-dcrup-dkim-crypto-06"> draft-ietf-dcrup-dkim-crypto-06 </option> <option value="draft-ietf-dcrup-dkim-crypto-05"> draft-ietf-dcrup-dkim-crypto-05 </option> <option value="draft-ietf-dcrup-dkim-crypto-04"> draft-ietf-dcrup-dkim-crypto-04 </option> <option value="draft-ietf-dcrup-dkim-crypto-03"> draft-ietf-dcrup-dkim-crypto-03 </option> <option value="draft-ietf-dcrup-dkim-crypto-02"> draft-ietf-dcrup-dkim-crypto-02 </option> <option value="draft-ietf-dcrup-dkim-crypto-01"> draft-ietf-dcrup-dkim-crypto-01 </option> <option value="draft-ietf-dcrup-dkim-crypto-00"> draft-ietf-dcrup-dkim-crypto-00 </option> </select> <button type="submit" class="btn btn-primary btn-sm" value="--html" name="difftype"> Side-by-side </button> <button type="submit" class="btn btn-primary btn-sm" value="--hwdiff" name="difftype"> Inline </button> </form> </td> </tr> <tr> <td></td> <th scope="row">Author</th> <td class="edit"> </td> <td> <span ><a title="Datatracker profile of John R. Levine" href="/person/ietf@johnlevine.com" >John R. Levine</a> <a href="mailto:ietf%40johnlevine.com" aria-label="Compose email to ietf@johnlevine.com" title="Compose email to ietf@johnlevine.com"> <i class="bi bi-envelope"></i></a></span> <br> <a class="btn btn-primary btn-sm mt-1" href="mailto:rfc8463@ietf.org?subject=rfc8463" title="Send email to the document authors">Email authors</a> </td> </tr> <tr> <td></td> <th scope="row"> RFC stream </th> <td class="edit"> </td> <td > <img alt="IETF Logo" class="d-lm-none w-25 mt-1" src="https://static.ietf.org/dt/12.28.2/ietf/images/ietf-logo-nor-white.svg" > <img alt="IETF Logo" class="d-dm-none w-25 mt-1" src="https://static.ietf.org/dt/12.28.2/ietf/images/ietf-logo-nor.svg" > </td> </tr> <tr> <td></td> <th scope="row"> Other formats </th> <td class="edit"> </td> <td> <div class="buttonlist"> <a class="btn btn-primary btn-sm" target="_blank" href="https://www.rfc-editor.org/rfc/rfc8463.txt"> <i class="bi bi-file-text"></i> txt </a> <a class="btn btn-primary btn-sm" target="_blank" href="https://www.rfc-editor.org/rfc/rfc8463.html"> <i class="bi bi-file-code"></i> html </a> <a class="btn btn-primary btn-sm" download="rfc8463.pdf" target="_blank" href="https://www.rfc-editor.org/rfc/pdfrfc/rfc8463.txt.pdf"> <i class="bi bi-file-pdf"></i> pdf </a> <a class="btn btn-primary btn-sm" target="_blank" href="/doc/rfc8463/bibtex/"> <i class="bi bi-file-ruled"></i> bibtex </a> </div> </td> </tr> <tr> <td> </td> <th scope="row"> Additional resources </th> <td class="edit"> </td> <td> <a href="https://mailarchive.ietf.org/arch/browse/dcrup/?q=rfc8463 OR %22draft-ietf-dcrup-dkim-crypto%22"> Mailing list discussion </a> </td> </tr> </tbody> </table> <a class="btn btn-sm btn-warning mb-3" target="_blank" href="https://github.com/ietf-tools/datatracker/issues/new/choose"> Report a datatracker bug <i class="bi bi-bug"></i> </a> </div> <div class="tab-pane mb-5" id="toc-tab-pane" role="tabpanel" aria-labelledby="toc-tab" tabindex="0"> <nav class="nav nav-pills flex-column small" id="toc-nav"> </nav> </div> <div class="tab-pane mb-5 small" id="pref-tab-pane" role="tabpanel" aria-labelledby="pref-tab" tabindex="0"> <label class="form-label fw-bold mb-2">Show sidebar by default</label> <div class="btn-group-vertical btn-group-sm d-flex" role="group"> <input type="radio" class="btn-check" name="sidebar" id="on-radio"> <label class="btn btn-outline-primary" for="on-radio">Yes</label> <input type="radio" class="btn-check" name="sidebar" id="off-radio"> <label class="btn btn-outline-primary" for="off-radio">No</label> </div> <label class="form-label fw-bold mt-4 mb-2">Tab to show by default</label> <div class="btn-group-vertical btn-group-sm d-flex" role="group"> <input type="radio" class="btn-check" name="deftab" id="docinfo-radio"> <label class="btn btn-outline-primary" for="docinfo-radio"> <i class="bi bi-info-circle me-1"></i>Info </label> <input type="radio" class="btn-check" name="deftab" id="toc-radio"> <label class="btn btn-outline-primary" for="toc-radio"> <i class="bi bi-list-ol me-1"></i>Contents </label> </div> <label class="form-label fw-bold mt-4 mb-2">HTMLization configuration</label> <div class="btn-group-vertical btn-group-sm d-flex" role="group"> <input type="radio" class="btn-check" name="htmlconf" id="txt-radio"> <label class="btn btn-outline-primary" for="txt-radio" title="This is the traditional HTMLization method."> <i class="bi bi-badge-sd me-1"></i>HTMLize the plaintext </label> <input type="radio" class="btn-check" name="htmlconf" id="html-radio"> <label class="btn btn-outline-primary" for="html-radio" title="This is the modern HTMLization method."> <i class="bi bi-badge-hd me-1"></i>Plaintextify the HTML </label> </div> <label class="form-label fw-bold mt-4 mb-2" for="ptsize">Maximum font size</label> <input type="range" class="form-range" min="7" max="16" id="ptsize" oninput="ptdemo.value = ptsize.value"> <label class="form-label fw-bold mt-4 mb-2">Page dependencies</label> <div class="btn-group-vertical btn-group-sm 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RFC 8463 - A New Cryptographic Signature Method for DomainKeys Identified Mail (DKIM)