if isEncrypted {
			dec, err := decrypt(oi.Parts[firstPartIdx].Index)
			if err == nil {
				// Load Index
				var idx s2.Index
				_, err := idx.Load(s2.RestoreIndexHeaders(dec))

				// Find compressed/uncompressed offsets of our partskip
				compOff, uCompOff, err2 := idx.Find(partSkip)

				if err == nil && err2 == nil && compOff > 0 {
					// Encrypted.