diff --git a/include/mbedtls/asn1write.h b/include/mbedtls/asn1write.h
index da73759..3c5072c 100644
--- a/include/mbedtls/asn1write.h
+++ b/include/mbedtls/asn1write.h
@@ -164,6 +164,27 @@
                                             size_t par_len);
 
 /**
+ * \brief           Write an AlgorithmIdentifier sequence in ASN.1 format.
+ *
+ * \note            This function works backwards in data buffer.
+ *
+ * \param p         The reference to the current position pointer.
+ * \param start     The start of the buffer, for bounds-checking.
+ * \param oid       The OID of the algorithm to write.
+ * \param oid_len   The length of the algorithm's OID.
+ * \param par_len   The length of the parameters, which must be already written.
+ * \param has_par   If there are any parameters. If 0, par_len must be 0. If 1
+ *                  and \p par_len is 0, NULL parameters are added.
+ *
+ * \return          The number of bytes written to \p p on success.
+ * \return          A negative \c MBEDTLS_ERR_ASN1_XXX error code on failure.
+ */
+int mbedtls_asn1_write_algorithm_identifier_ext(unsigned char **p,
+                                                const unsigned char *start,
+                                                const char *oid, size_t oid_len,
+                                                size_t par_len, int has_par);
+
+/**
  * \brief           Write a boolean tag (#MBEDTLS_ASN1_BOOLEAN) and value
  *                  in ASN.1 format.
  *
diff --git a/include/mbedtls/oid.h b/include/mbedtls/oid.h
index a72f51c..1cbf968 100644
--- a/include/mbedtls/oid.h
+++ b/include/mbedtls/oid.h
@@ -90,6 +90,9 @@
 #define MBEDTLS_OID_OIW_SECSIG                  MBEDTLS_OID_ORG_OIW "\x03"
 #define MBEDTLS_OID_OIW_SECSIG_ALG              MBEDTLS_OID_OIW_SECSIG "\x02"
 #define MBEDTLS_OID_OIW_SECSIG_SHA1             MBEDTLS_OID_OIW_SECSIG_ALG "\x1a"
+#define MBEDTLS_OID_ORG_THAWTE                  "\x65"          /* thawte(101) */
+#define MBEDTLS_OID_THAWTE                      MBEDTLS_OID_ISO_IDENTIFIED_ORG \
+        MBEDTLS_OID_ORG_THAWTE
 #define MBEDTLS_OID_ORG_CERTICOM                "\x81\x04"  /* certicom(132) */
 #define MBEDTLS_OID_CERTICOM                    MBEDTLS_OID_ISO_IDENTIFIED_ORG \
         MBEDTLS_OID_ORG_CERTICOM
@@ -437,6 +440,15 @@
  *   ecdsa-with-SHA2(3) 4 } */
 #define MBEDTLS_OID_ECDSA_SHA512            MBEDTLS_OID_ANSI_X9_62_SIG_SHA2 "\x04"
 
+/*
+ * EC key algorithms from RFC 8410
+ */
+
+#define MBEDTLS_OID_X25519                  MBEDTLS_OID_THAWTE "\x6e" /**< id-X25519    OBJECT IDENTIFIER ::= { 1 3 101 110 } */
+#define MBEDTLS_OID_X448                    MBEDTLS_OID_THAWTE "\x6f" /**< id-X448      OBJECT IDENTIFIER ::= { 1 3 101 111 } */
+#define MBEDTLS_OID_ED25519                 MBEDTLS_OID_THAWTE "\x70" /**< id-Ed25519   OBJECT IDENTIFIER ::= { 1 3 101 112 } */
+#define MBEDTLS_OID_ED448                   MBEDTLS_OID_THAWTE "\x71" /**< id-Ed448     OBJECT IDENTIFIER ::= { 1 3 101 113 } */
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -531,6 +543,30 @@
  */
 int mbedtls_oid_get_oid_by_ec_grp(mbedtls_ecp_group_id grp_id,
                                   const char **oid, size_t *olen);
+
+/**
+ * \brief          Translate AlgorithmIdentifier OID into an EC group identifier,
+ *                 for curves that are directly encoded at this level
+ *
+ * \param oid      OID to use
+ * \param grp_id   place to store group id
+ *
+ * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ */
+int mbedtls_oid_get_ec_grp_algid(const mbedtls_asn1_buf *oid, mbedtls_ecp_group_id *grp_id);
+
+/**
+ * \brief          Translate EC group identifier into AlgorithmIdentifier OID,
+ *                 for curves that are directly encoded at this level
+ *
+ * \param grp_id   EC group identifier
+ * \param oid      place to store ASN.1 OID string pointer
+ * \param olen     length of the OID
+ *
+ * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ */
+int mbedtls_oid_get_oid_by_ec_grp_algid(mbedtls_ecp_group_id grp_id,
+                                        const char **oid, size_t *olen);
 #endif /* MBEDTLS_ECP_LIGHT */
 
 /**