diff --git a/library/hash_info.h b/library/hash_info.h
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--- /dev/null
+++ b/library/hash_info.h
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+/**
+ * Hash information that's independent from the crypto implementation.
+ *
+ *  This can be used by:
+ *  - code based on PSA
+ *  - code based on the legacy API
+ *  - code based on either of them depending on MBEDTLS_USE_PSA_CRYPTO
+ *  - code based on either of them depending on what's available
+ *
+ *  Note: this internal module will go away when everything become based on
+ *  PSA Crypto; it is a helper for the transition while hash algorithms are
+ *  wtill represented using mbedtls_md_type_t in most places even when PSA is
+ *  used for the actual crypto computations.
+ *
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+#ifndef MBEDTLS_HASH_INFO_H
+#define MBEDTLS_HASH_INFO_H
+
+#include "common.h"
+
+#include "mbedtls/md.h"
+#include "psa/crypto.h"
+
+/** Get the output length of the given hash type from its MD type.
+ *
+ * \note To get the output length from the PSA alg, use \c PSA_HASH_LENGTH().
+ *
+ * \param md_type   The hash MD type.
+ *
+ * \return          The output length in bytes, or 0 if not known.
+ */
+unsigned char mbedtls_hash_info_get_size( mbedtls_md_type_t md_type );
+
+/** Get the block size of the given hash type from its MD type.
+ *
+ * \note To get the output length from the PSA alg, use
+ *       \c PSA_HASH_BLOCK_LENGTH().
+ *
+ * \param md_type   The hash MD type.
+ *
+ * \return          The block size in bytes, or 0 if not known.
+ */
+unsigned char mbedtls_hash_info_get_block_size( mbedtls_md_type_t md_type );
+
+/** Get the PSA alg from the MD type.
+ *
+ * \param md_type   The hash MD type.
+ *
+ * \return          The corresponding PSA algorithm identifier,
+ *                  or PSA_ALG_NONE if not known.
+ */
+psa_algorithm_t mbedtls_hash_info_psa_from_md( mbedtls_md_type_t md_type );
+
+/** Get the MD type alg from the PSA algorithm identifier.
+ *
+ * \param psa_alg   The PSA hash algorithm.
+ *
+ * \return          The corresponding MD type,
+ *                  or MBEDTLS_MD_NONE if not known.
+ */
+mbedtls_md_type_t mbedtls_hash_info_md_from_psa( psa_algorithm_t psa_alg );
+
+#endif /* MBEDTLS_HASH_INFO_H */