[taler-anastasis] branch master updated: sort out HKDF invocations (salt vs ikm vs info)

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dold pushed a commit to branch master
in repository anastasis.

The following commit(s) were added to refs/heads/master by this push:
     new 0120fe8  sort out HKDF invocations (salt vs ikm vs info)
0120fe8 is described below

commit 0120fe8345d6592bd61c0ae4df1c3db34155715c
Author: Florian Dold <florian@dold.me>
AuthorDate: Tue Oct 19 14:07:27 2021 +0200

    sort out HKDF invocations (salt vs ikm vs info)
---
 src/util/anastasis_crypto.c | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/util/anastasis_crypto.c b/src/util/anastasis_crypto.c
index e122c07..f5e6c77 100644
--- a/src/util/anastasis_crypto.c
+++ b/src/util/anastasis_crypto.c
@@ -61,12 +61,15 @@ ANASTASIS_CRYPTO_secure_answer_hash (
                  GNUNET_CRYPTO_kdf (
                    result,
                    sizeof (*result),
-                   "Anastasis-secure-question-uuid-salting",
-                   strlen ("Anastasis-secure-question-uuid-salting"),
-                   &pow,
-                   sizeof (pow),
+                   /* salt / XTS */
                    uuid,
                    sizeof (*uuid),
+                   /* skm */
+                   &pow,
+                   sizeof (pow),
+                   /* info chunks */
+                   "anastasis-secure-question-hashing",
+                   strlen ("anastasis-secure-question-hashing"),
                    NULL,
                    0));
 }
@@ -88,14 +91,19 @@ derive_key (const void *key_material,
             const char *salt,
             struct ANASTASIS_CRYPTO_SymKeyP *key)
 {
-
   if (GNUNET_YES !=
       GNUNET_CRYPTO_kdf (key,
                          sizeof (struct ANASTASIS_CRYPTO_SymKeyP),
+                         /* salt / XTS */
                          nonce,
                          sizeof (struct ANASTASIS_CRYPTO_NonceP),
+                         /* ikm */
                          key_material,
                          key_m_len,
+                         /* info chunks */
+                         /* The "salt" passed here is actually not something 
random,
+                            but a protocol-specific identifier string.  Thus
+                            we pass it as a context info to the HKDF */
                          salt,
                          strlen (salt),
                          NULL,
@@ -230,8 +238,13 @@ ANASTASIS_CRYPTO_account_private_key_derive (
   if (GNUNET_YES !=
       GNUNET_CRYPTO_kdf (&priv_key->priv,
                          sizeof (priv_key->priv),
+                         /* salt / XTS */
+                         NULL,
+                         0,
+                         /* ikm */
                          id,
                          sizeof (struct ANASTASIS_CRYPTO_UserIdentifierP),
+                         /* context chunks */
                          "ver",
                          strlen ("ver"),
                          NULL,
@@ -422,10 +435,15 @@ ANASTASIS_CRYPTO_policy_key_derive (
 {
   GNUNET_CRYPTO_kdf (policy_key,
                      sizeof (*policy_key),
-                     key_shares,
-                     keyshare_length * sizeof (*key_shares),
+                     /* salt / XTS */
                      salt,
                      sizeof (*salt),
+                     /* ikm */
+                     key_shares,
+                     keyshare_length * sizeof (*key_shares),
+                     /* info chunks */
+                     "anastasis-policy-key-derive",
+                     strlen ("anastasis-policy-key-derive"),
                      NULL, 0);
 }
 

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