docs: add missing documentation for BlobKey and BlobHeader.BlobKey()

core/v2/serialization.go

@@ -27,6 +27,9 @@ type abiBlobCommitments struct {
 	DataLength       uint32
 }
 
+// BlobKey serializes the BlobHeader into a 32-byte unique identifier.
+// This serialization must ALWAYS match the serialization that we perform onchain:
+// https://github.com/Layr-Labs/eigenda/blob/a6dd724acdf732af483fd2d9a86325febe7ebdcd/contracts/src/libraries/EigenDAHasher.sol#L119
 func (b *BlobHeader) BlobKey() (BlobKey, error) {
 	versionType, err := abi.NewType("uint16", "", nil)
 	if err != nil {

core/v2/types.go

@@ -31,6 +31,17 @@ func (c *Assignment) GetIndices() []uint32 {
 	return indices
 }
 
+// BlobKey is the unique identifier for a blob dispersal.
+//
+// It is computed as the Keccak256 hash of some serialization of the blob header
+// where the PaymentHeader has been replaced with Hash(PaymentHeader), in order
+// to be easily verifiable onchain. See the BlobKey method of BlobHeader for more
+// details.
+//
+// It can be used to retrieve a blob from relays.
+//
+// Note that two blobs can have the same content but different headers,
+// so they are allowed to both exist in the system.
 type BlobKey [32]byte
 
 func (b BlobKey) Hex() string {