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feat: added config member to store block number for hign part of ecdsa key

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nilesh.kale
2025-07-21 15:40:52 +05:30
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docs/en/api-reference/peripherals/ecdsa.rst
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@@ -25,46 +25,27 @@ On {IDF_TARGET_NAME}, the ECDSA module works with a secret key burnt into an eFu
ECDSA Key Storage
^^^^^^^^^^^^^^^^^
ECDSA private keys are stored in eFuse key blocks. The number of key blocks required depends on the curve size:
.. only:: SOC_ECDSA_SUPPORT_CURVE_P384
- **P-192 and P-256 curves**: Require one eFuse key block (256 bits)
- **P-384 curve**: Requires two eFuse key blocks (512 bits total)
ECDSA private keys are stored in eFuse key blocks. The number of key blocks required depends on the curve size:
When using the P-384 curve or any other curves that require two key blocks, you must use the appropriate macro to combine the block numbers into a single integer that the ECDSA peripheral can understand:
- **P-256 curve**: Require one eFuse key block (256 bits)
- **P-384 curve**: Requires two eFuse key blocks (512 bits total)
- **For mbedTLS applications**: Use :c:macro:`MBEDTLS_ECDSA_COMBINE_KEY_BLOCKS` macro (defined in ``ecdsa/ecdsa_alt.h``)
- **For HAL applications**: Use :c:macro:`HAL_ECDSA_COMBINE_KEY_BLOCKS` macro (defined in ``hal/ecdsa_types.h``)
- **For ESP-TLS applications**: Use :c:macro:`ESP_TLS_ECDSA_COMBINE_KEY_BLOCKS` macro (defined in ``esp_tls.h``)
For curves requiring two key blocks (like P-384), configure the following fields:
You can also extract the individual block numbers using the corresponding extract macro:
- Set :cpp:member:`esp_tls_cfg_t::ecdsa_key_efuse_blk` to the low block number
- Set :cpp:member:`esp_tls_cfg_t::ecdsa_key_efuse_blk_high` to the high block number
- **For mbedTLS applications**: Use :c:macro:`MBEDTLS_ECDSA_EXTRACT_KEY_BLOCKS` macro
- **For HAL applications**: Use :c:macro:`HAL_ECDSA_EXTRACT_KEY_BLOCKS` macro
- **For ESP-TLS applications**: Use :c:macro:`ESP_TLS_ECDSA_EXTRACT_KEY_BLOCKS` macro
For single-block curves (like P-256), only set :cpp:member:`esp_tls_cfg_t::ecdsa_key_efuse_blk` and leave :cpp:member:`esp_tls_cfg_t::ecdsa_key_efuse_blk_high` as 0 or unassigned.
Here is an example of how to use these macros:
.. only:: not SOC_ECDSA_SUPPORT_CURVE_P384
.. code-block:: c
ECDSA private keys are stored in eFuse key blocks. One eFuse key block (256 bits) is required for P-256 curve.
#include "ecdsa/ecdsa_alt.h"
Configure the following field:
// Example: Using P-384 curve which requires two key blocks
// Assuming you want to use key blocks 4 and 5
uint8_t block_low = 4; // Lower key block
uint8_t block_high = 5; // Higher key block
// Combine the two block numbers into a single integer
// Note: First parameter is high block, second parameter is low block
uint16_t combined_blocks = MBEDTLS_ECDSA_COMBINE_KEY_BLOCKS(block_high, block_low);
// Use the combined_blocks value in your ECDSA operations
// This value can be passed to mbedTLS ECDSA functions
// To extract the individual block numbers later
uint8_t extracted_block_low, extracted_block_high;
MBEDTLS_ECDSA_EXTRACT_KEY_BLOCKS(combined_blocks, &extracted_block_high, &extracted_block_low);
// extracted_block_low will be 4, extracted_block_high will be 5
- Set :cpp:member:`esp_tls_cfg_t::ecdsa_key_efuse_blk` to the block number and leave :cpp:member:`esp_tls_cfg_t::ecdsa_key_efuse_blk_high` as 0 or unassigned.
ECDSA key can be programmed externally through ``idf.py`` script. Here is an example of how to program the ECDSA key: