SIMD-0317: Enforce 32 data + 32 coding shreds

proposals/0317-enforce-32-data-shreds.md

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+---
+simd: '0317'
+title: Enforce 32 data + 32 coding shreds
+authors:
+  - Emanuele Cesena
+category: Standard
+type: Core
+status: Review
+created: 2025-07-08
+feature:
+---
+
+## Summary
+
+All clients currently send 32 data + 32 coding shreds, however Turbine still allows
+to send and receive a variable number of shreds. With this change we will enforce
+sending and receiving only 32 data + 32 coding shreds.
+
+## Motivation
+
+It is inconvinient to support many combinations of data + coding shreds.
+There's no security benefit, and in fact security is reduced when the number of
+shreds is low.
+
+## New Terminology
+
+N/A
+
+## Detailed Design
+
+A sender should always produce 32 data shreds + 32 coding shreds per FEC set
+(this is currently already happening).
+
+Receivers currently accept FEC sets with variable number of shreds.
+
+If `enforce_32_data_shreds: <PUBKEY>`
+is active, then any FEC set with a number of shreds different than 32 data + 32 coding
+will be dropped on ingest.
+
+## Alternatives Considered
+
+Leave as is.
+
+## Impact
+
+Clients will no longer accept FEC sets (thus blocks) with any number of shreds
+different than 32 data + 32 coding.
+
+## Security Considerations
+
+Security is improved since the (minimum) number of shreds is now 32 + 32.
+
+## Backwards Compatibility
+
+This feature is not backwards compatible.