[lsd0001] branch master updated: simplify crypto remove ZKDF-Private

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martin-schanzenbach pushed a commit to branch master
in repository lsd0001.

The following commit(s) were added to refs/heads/master by this push:
     new 3324e16  simplify crypto remove ZKDF-Private
3324e16 is described below

commit 3324e16553dad65fc44ee96986051cfdd44cec88
Author: Martin Schanzenbach <schanzen@gnunet.org>
AuthorDate: Sat Mar 26 09:55:49 2022 +0100

    simplify crypto remove ZKDF-Private
---
 draft-schanzen-gns.xml | 97 ++++++++++++++------------------------------------
 1 file changed, 27 insertions(+), 70 deletions(-)

diff --git a/draft-schanzen-gns.xml b/draft-schanzen-gns.xml
index 10ba55a..a57ca8f 100644
--- a/draft-schanzen-gns.xml
+++ b/draft-schanzen-gns.xml
@@ -1,4 +1,4 @@
-<?xml version='1.0' encoding='utf-8'?>
+<?xml version='1.0' encoding='utf-8'?
 <!DOCTYPE rfc SYSTEM "rfc2629-xhtml.ent" [
 <!ENTITY RFC1034 PUBLIC '' 
"http://xml.resource.org/public/rfc/bibxml/reference.RFC.1034.xml";>
 <!ENTITY RFC1035 PUBLIC '' 
"http://xml.resource.org/public/rfc/bibxml/reference.RFC.1035.xml";>
@@ -281,8 +281,7 @@
        </dd>
        <dt>Zone Key Derivation Function</dt>
        <dd>
-         The zone key derivation function (ZKDF) blinds a key using a label.
-         There are different functions for public and private keys, 
respectively.
+         The zone key derivation function (ZKDF) blinds a zone key using a 
label.
        </dd>
        <dt>Zone Owner</dt>
        <dd>
@@ -453,15 +452,7 @@
          is a function to generate a new private key d and
         the corresponding public zone key zk.
        </dd>
-       <dt>ZKDF-Private(d,label) -> d'</dt>
-       <dd>
-         is a zone key derivation function which blinds a private key d
-         using label, resulting in another private key which
-         can be used to create cryptographic signatures.
-         GNS only requires a signature to be created directly with
-         d to sign a revocation message for the zone key zk.
-       </dd>
-       <dt>ZKDF-Public(zk,label) -> zk'</dt>
+       <dt>ZKDF(zk,label) -> zk'</dt>
        <dd>
          is a zone key derivation function which blinds a zone key zk
          using a label. zk and zk' must be unlinkable. Furthermore,
@@ -502,7 +493,7 @@
        <dt>SignDerived(d,label,message) -> signature</dt>
        <dd>
          is a function to sign a message (typically encrypted record data) that
-         can be verified using the derived zone key zk' := 
ZKDF-Public(zk,label).
+         can be verified using the derived zone key zk' := ZKDF(zk,label).
          In order to leverage performance-enhancing caching features of certain
          underlying storages, in particular DHTs, a deterministic signature
          scheme is recommended.
@@ -510,7 +501,7 @@
        <dt>VerifyDerived(zk,label,message,signature) -> boolean</dt>
        <dd>
          is function to verify the signature using the derived zone key
-         zk' := ZKDF-Public(zk,label).
+         zk' := ZKDF(zk,label).
          The function returns a boolean value of "TRUE" if the signature is 
valid,
          and otherwise "FALSE".
        </dd>
@@ -1068,25 +1059,11 @@ zTLD[126..129].zTLD[63..125].zTLD[0..62]
          The zone type and zone key of a PKEY are 4 + 32 bytes in length. This 
means that
          a zTLD will always fit into a single label and does
          not need any further conversion.
-       </t>
-       <t>
-         Given a label, the output d' of the ZKDF-Private(d,label) function 
for zone
-         key blinding is calculated as follows for PKEY zones:
-       </t>
-       <artwork name="" type="" align="left" alt=""><![CDATA[
-ZKDF-Private(d,label):
-  zk := d * G
-  PRK_h := HKDF-Extract ("key-derivation", zk)
-  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
-  d' := (h * d) mod L
-  return d'
-        ]]></artwork>
-       <t>
-         Equally, given a label, the output zk' of the ZKDF-Public(zk,label) 
function is
+         Given a label, the output zk' of the ZKDF(zk,label) function is
          calculated as follows for PKEY zones:
        </t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
-ZKDF-Public(zk,label):
+ZKDF(zk,label):
   PRK_h := HKDF-Extract ("key-derivation", zk)
   h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
   zk' := (h mod L) * zk
@@ -1113,7 +1090,10 @@ ZKDF-Public(zk,label):
        </t>
          <artwork name="" type="" align="left" alt=""><![CDATA[
 SignDerived(d,label,message):
-  d' := ZKDF-Private(d,label)
+  zk := d * G
+  PRK_h := HKDF-Extract ("key-derivation", zk)
+  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
+  d' := (h * d) mod L
   return Sign(d',message)
            ]]></artwork>
          <t>
@@ -1121,7 +1101,7 @@ SignDerived(d,label,message):
          </t>
          <artwork name="" type="" align="left" alt=""><![CDATA[
 VerifyDerived(zk,label,message,signature):
-  zk' := ZKDF-Public(zk,label)
+  zk' := ZKDF(zk,label)
   return Verify(zk',message,signature)
            ]]></artwork>
        <t>
@@ -1265,37 +1245,11 @@ S-Decrypt(zk,label,expiration,ciphertext):
          <t>
            The "EDKEY" ZKDF instantiation is based on <xref target="Tor224"/>.
            The calculation of a is defined in Section 5.1.5 of <xref 
target="RFC8032" />.
-           Given a label, the output of the ZKDF-Private function for zone
-           key blinding is calculated as follows:
-         </t>
-         <artwork name="" type="" align="left" alt=""><![CDATA[
-ZKDF-Private(d,label):
-  /* EdDSA clamping */
-  dh := SHA-512 (d)
-  a := dh[0..31]
-  a[0] &= 248
-  a[31] &= 127
-  a[31] |= 64
-  /* Calculate zk corresponding to d */
-  zk := a * G
-
-  /* Calculate the blinding factor h */
-  PRK_h := HKDF-Extract ("key-derivation", zk)
-  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
-  /* Ensure that h == h mod L */
-  h[31] &= 7
-
-  a1 := a >> 3
-  a2 := (h * a1) mod L
-  d' := a2 << 3
-  return d'
-           ]]></artwork>
-         <t>
-           Equally, given a label, the output of the ZKDF-Public function is
+           Given a label, the output of the ZKDF function is
            calculated as follows:
          </t>
          <artwork name="" type="" align="left" alt=""><![CDATA[
-ZKDF-Public(zk,label):
+ZKDF(zk,label):
   /* Calculate the blinding factor */
   PRK_h := HKDF-Extract ("key-derivation", zk)
   h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
@@ -1339,9 +1293,9 @@ ZKDF-Public(zk,label):
            be implemented as defined in <xref target="RFC8032" />.
          </t>
          <t>
-           Signatures for EDKEY zones using the derived private scalar d'
-           are not compliant with <xref target="RFC8032" />.
-           As the corresponding private key to the derived private scalar d'
+           Signatures for EDKEY zones use a derived private scalar d'
+           which is not compliant with <xref target="RFC8032" />.
+           As the corresponding private key to the derived private scalar
            is not known, it is not possible to deterministically derive the
            signature part R according to <xref target="RFC8032" />.
            Instead, signatures <bcp14>MUST</bcp14> be generated as follows for 
any given
@@ -1368,9 +1322,13 @@ SignDerived(d,label,message):
   /* Calculate blinding factor */
   PRK_h := HKDF-Extract ("key-derivation", zk)
   h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
+  /* Ensure that h == h mod L */
+  h[31] &= 7
 
-  d' := ZKDF-Private(d,label)
   zk' := h * zk
+  a1 := a >> 3
+  a2 := (h * a1) mod L
+  d' := a2 << 3
   nonce := SHA-256 (dh[32..63] || h)
   r := SHA-512 (nonce || message)
   R := r * G
@@ -1382,7 +1340,7 @@ SignDerived(d,label,message):
          </t>
          <artwork name="" type="" align="left" alt=""><![CDATA[
 VerifyDerived(zk,label,message,signature):
-  zk' := ZKDF-Public(zk,label)
+  zk' := ZKDF(zk,label)
   (R,S) := signature
   return S * G == R + SHA-512(R, zk', message) * zk'
            ]]></artwork>
@@ -1779,7 +1737,7 @@ GET(key) -> value
          Given a label, the storage key q is derived as follows:
        </t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
-q := SHA-512 (ZKDF-Public(zk, label))
+q := SHA-512 (ZKDF(zk, label))
          ]]></artwork>
        <dl>
          <dt>label</dt>
@@ -1851,7 +1809,7 @@ q := SHA-512 (ZKDF-Public(zk, label))
          </dd>
          <dt>ZONE KEY</dt>
          <dd>
-           is the blinded zone key "ZKDF-Public(zk, label)"
+           is the blinded zone key "ZKDF(zk, label)"
            to be used to verify SIGNATURE.
            The length and format of the public key depends on the ztype.
          </dd>
@@ -1860,9 +1818,8 @@ q := SHA-512 (ZKDF-Public(zk, label))
            The signature is computed over the EXPIRATION and BDATA fields
            as detailed in <xref target="figure_rrsigwithpseudo"/>.
            The length and format of the signature depends on the ztype.
-           The signature is created using the Sign() function of
-           the cryptosystem of the zone and the derived private key
-           "ZKDF-Private(d, label)" (see <xref target="zones" />).
+           The signature is created using the SignDerived() function of
+           the cryptosystem of the zone (see <xref target="zones" />).
          </dd>
          <dt>EXPIRATION</dt>
          <dd>

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