Clarify documentation about default HKDF salt value.

PiperOrigin-RevId: 507991558
Alan-love · Feb 8, 2023 · 7948b63 · 7948b63
1 parent da4e3f3
commit 7948b63
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Showing 5 changed files with 30 additions and 10 deletions.
diff --git a/cc/proto/hkdf_prf.proto b/cc/proto/hkdf_prf.proto
@@ -26,8 +26,12 @@ option go_package = "github.com/google/tink/proto/hkdf_prf_proto";
 
 message HkdfPrfParams {
   HashType hash = 1;
-  // Salt, optional in RFC 5869. Using "" is equivalent to zeros of length up to
-  // the block length of the HMac.
+  // Optional.
+  //
+  // An unspecified or zero-length value is equivalent to a sequence of zeros
+  // (0x00) with a length equal to the output size of hash.
+  //
+  // See https://rfc-editor.org/rfc/rfc5869.
   bytes salt = 2;
 }
 

diff --git a/java_src/proto/hkdf_prf.proto b/java_src/proto/hkdf_prf.proto
@@ -26,8 +26,12 @@ option go_package = "github.com/google/tink/proto/hkdf_prf_proto";
 
 message HkdfPrfParams {
   HashType hash = 1;
-  // Salt, optional in RFC 5869. Using "" is equivalent to zeros of length up to
-  // the block length of the HMac.
+  // Optional.
+  //
+  // An unspecified or zero-length value is equivalent to a sequence of zeros
+  // (0x00) with a length equal to the output size of hash.
+  //
+  // See https://rfc-editor.org/rfc/rfc5869.
   bytes salt = 2;
 }
 

diff --git a/javascript/proto/hkdf_prf.proto b/javascript/proto/hkdf_prf.proto
@@ -26,8 +26,12 @@ option go_package = "github.com/google/tink/proto/hkdf_prf_proto";
 
 message HkdfPrfParams {
   HashType hash = 1;
-  // Salt, optional in RFC 5869. Using "" is equivalent to zeros of length up to
-  // the block length of the HMac.
+  // Optional.
+  //
+  // An unspecified or zero-length value is equivalent to a sequence of zeros
+  // (0x00) with a length equal to the output size of hash.
+  //
+  // See https://rfc-editor.org/rfc/rfc5869.
   bytes salt = 2;
 }
 

diff --git a/proto/hkdf_prf.proto b/proto/hkdf_prf.proto
@@ -26,8 +26,12 @@ option go_package = "github.com/google/tink/proto/hkdf_prf_proto";
 
 message HkdfPrfParams {
   HashType hash = 1;
-  // Salt, optional in RFC 5869. Using "" is equivalent to zeros of length up to
-  // the block length of the HMac.
+  // Optional.
+  //
+  // An unspecified or zero-length value is equivalent to a sequence of zeros
+  // (0x00) with a length equal to the output size of hash.
+  //
+  // See https://rfc-editor.org/rfc/rfc5869.
   bytes salt = 2;
 }
 

diff --git a/python/tink/proto/hkdf_prf.proto b/python/tink/proto/hkdf_prf.proto
@@ -26,8 +26,12 @@ option go_package = "github.com/google/tink/proto/hkdf_prf_proto";
 
 message HkdfPrfParams {
   HashType hash = 1;
-  // Salt, optional in RFC 5869. Using "" is equivalent to zeros of length up to
-  // the block length of the HMac.
+  // Optional.
+  //
+  // An unspecified or zero-length value is equivalent to a sequence of zeros
+  // (0x00) with a length equal to the output size of hash.
+  //
+  // See https://rfc-editor.org/rfc/rfc5869.
   bytes salt = 2;
 }