Mbed TLS (TF-PSA-Crypto)

Facts and the checks behind them

Nothing below is copied from documentation. The check content/libraries/verify/mbedtls/run.sh ran Mbed TLS (TF-PSA-Crypto) 4.1.1 in the container image alpine:3.24.2 on October 20, 2026; the page must match what it printed, and each fact lists those lines.

• ECDSA signature encoding

  raw

  psa_sign_message returned 64 bytes of raw r‖s on P-256.

  Recorded by the check

  fact ecdsa-signature-encoding = raw
  evidence ecdsa-signature-encoding: psa_sign_message returned 64 bytes

• ECDSA nonce

  rfc6979-opt-in

  PSA_ALG_ECDSA uses a random nonce; PSA_ALG_DETERMINISTIC_ECDSA reproduced RFC 6979 appendix A.2.5.

  Recorded by the check

  fact ecdsa-nonce = rfc6979-opt-in
  evidence ecdsa-nonce: PSA_ALG_ECDSA repeats: no; PSA_ALG_DETERMINISTIC_ECDSA reproduces the RFC 6979 A.2.5 r: yes (status 0)

• Low-S when signing

  either

  s is not normalized: high-S values appeared among 64 signatures.

  Recorded by the check

  fact ecdsa-low-s-sign = either

• High-S when verifying

  accepts-high-s

  A signature with s replaced by n − s verified.

  Recorded by the check

  fact ecdsa-low-s-verify = accepts-high-s

• What the signing call hashes

  hashes-message-or-digest

  psa_sign_message hashes; psa_sign_hash signs a digest, and that signature verified with psa_verify_message.

  Recorded by the check

  fact ecdsa-prehash = hashes-message-or-digest

• Malformed ECDSA signature

  returns-false

  A DER signature, a 3-byte blob and a valid signature over other data all returned PSA_ERROR_INVALID_SIGNATURE (-149).

  Recorded by the check

  fact ecdsa-malformed-signature = returns-false
  evidence ecdsa-malformed-signature: psa_verify_message status: DER -149, 3 bytes -149, wrong message -149 (PSA_ERROR_INVALID_SIGNATURE = -149)

• ECDSA curves

  P-256P-384P-521secp256k1brainpoolP256r1brainpoolP384r1brainpoolP512r1

  P-256, P-384, P-521, secp256k1 and brainpoolP256r1/P384r1/P512r1 signed and verified; P-224 key generation failed in this build.

  Recorded by the check

  fact ecdsa-curves = P-256, P-384, P-521, secp256k1, brainpoolP256r1, brainpoolP384r1, brainpoolP512r1

• EdDSA

  none

  Ed25519 key generation returned PSA_ERROR_NOT_SUPPORTED (-134).

  Recorded by the check

  fact eddsa = none
  evidence eddsa: psa_generate_key for an Ed25519 key: status -134

• Post-quantum algorithms

  LMS

  MBEDTLS_LMS_C is enabled (LMS signature verification); no ML-KEM or ML-DSA PSA key type is defined, and the experimental mldsa-native driver is not built.

  Recorded by the check

  fact pqc = LMS
  evidence pqc: MBEDTLS_LMS_C is enabled (LMS hash-based signature verification, <mbedtls/lms.h>)
  evidence pqc: no ML-DSA or ML-KEM PSA key type is defined in these headers
  evidence pqc: psa/crypto_config.h of this build: //#define TF_PSA_CRYPTO_PQCP_MLDSA_ENABLED;//#define TF_PSA_CRYPTO_PQCP_MLDSA_87_ENABLED (commented out = the experimental mldsa-native driver is not built)

• Public key formats

  spki-dersec1-uncompressed

  psa_export_public_key returns the 65-byte uncompressed SEC1 point; SPKI DER is written and parsed through the pk layer.

  Recorded by the check

  fact public-key-formats = spki-der, sec1-uncompressed
  evidence public-key-formats: psa_export_public_key returns 65 bytes starting 0x04 (an uncompressed SEC1 point)

Usage

#include <psa/crypto.h>
#include <stdio.h>

int main(void) {
    if (psa_crypto_init() != PSA_SUCCESS) return 1;
    /* The algorithm is part of the key policy: here deterministic ECDSA (RFC 6979) with SHA-256. */
    psa_algorithm_t alg = PSA_ALG_DETERMINISTIC_ECDSA(PSA_ALG_SHA_256);
    psa_key_attributes_t attr = PSA_KEY_ATTRIBUTES_INIT;
    psa_set_key_type(&attr, PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1));
    psa_set_key_bits(&attr, 256);
    psa_set_key_usage_flags(&attr, PSA_KEY_USAGE_SIGN_MESSAGE | PSA_KEY_USAGE_VERIFY_MESSAGE);
    psa_set_key_algorithm(&attr, alg);
    psa_key_id_t key;
    if (psa_generate_key(&attr, &key) != PSA_SUCCESS) return 1;

    const uint8_t msg[] = "order #1042 approved";
    uint8_t sig[PSA_SIGNATURE_MAX_SIZE];
    size_t sig_len;
    psa_sign_message(key, alg, msg, sizeof msg - 1, sig, sizeof sig, &sig_len);

    /* PSA signatures are raw r||s (64 bytes on P-256): wrap them in DER for X.509 or OpenSSL peers. */
    psa_status_t status = psa_verify_message(key, alg, msg, sizeof msg - 1, sig, sig_len);
    printf("signature bytes: %zu, verified: %d\n", sig_len, status == PSA_SUCCESS);
    psa_destroy_key(key);
    return 0;
}