DCMTK: ciphers.txt file

DCMTK Version 3.7.0 OFFIS DICOM Toolkit

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ciphers.txt file

    ============================
    CIPHERSUITE SUPPORT IN DCMTK
    ============================

    When compiled with OpenSSL support, several of the DCMTK network
    applications optionally support TLS encapsulated secure DICOM communication
    as defined in the DICOM Part 15. TLS (Transport Layer Security) can be
    used with different so-called "ciphersuites". Each ciphersuite defines

      - the algorithm to be used for the authentication of peers,
      - the algorithm to be used for key-exchange of session keys,
      - the algorithm to be used for bulk data encryption, and
      - the algorithm to be used for secure hash (message digest).

    The ciphersuites to be used for secure DICOM communication can be
    controlled in the TLS-enabled DCMTK tools, e.g. with appropriate command
    line parameters. The ciphersuite name constants known to DCMTK are
    exactly as defined in the RFCs that define the TLS protocol and its
    various extensions.

    The TLS protocol allows a dynamic negotiation of the ciphersuite to be used.
    For this purpose, the TLS-enabled DCMTK tools allow that multiple
    ciphersuites be specified. During negotiation, the TLS client proposes
    a list of ciphersuites that it supports, and the TLS server selects
    from this list. Many systems will select the first entry from the list
    that is also know to the server (thus respecting the prioritization
    of ciphersuites by the client), but servers may also select based
    on their own priorities, e.g. by always selecting the most secure ciphersuite.

    In DCMTK, the selection of ciphersuites is based on "TLS profiles", which
    follow the secure profiles define in DICOM Part 15:

    - BCP 195 RFC 8996 TLS Profile (default)
      This profile proposes the following set of ciphersuites:

      - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)

      This profile will support TLS 1.3 when compiled against OpenSSL 1.1.1
      or newer. In this case, the following TLS 1.3 ciphersuites will be
      proposed additionally:

      - TLS_AES_256_GCM_SHA384 (only TLS 1.3)
      - TLS_CHACHA20_POLY1305_SHA256 (only TLS 1.3)
      - TLS_AES_128_GCM_SHA256 (only TLS 1.3)
      - TLS_AES_128_CCM_SHA256 (only TLS 1.3)
      - TLS_AES_128_CCM_8_SHA256 (only TLS 1.3)

    - Modified BCP 195 RFC 8996 TLS Profile
      This profile proposes the following set of ciphersuites:

      - TLS_ECDHE_RSA_WITH_CAMELLIA_128_GCM_SHA256 (only TLS 1.2)*
      - TLS_ECDHE_ECDSA_WITH_CAMELLIA_128_GCM_SHA256 (only TLS 1.2)*
      - TLS_ECDHE_ECDSA_WITH_AES_128_CCM (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_CAMELLIA_256_GCM_SHA384 (only TLS 1.2)*
      - TLS_ECDHE_ECDSA_WITH_CAMELLIA_256_GCM_SHA384 (only TLS 1.2)*
      - TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256 (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_AES_256_CCM (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)

      - TLS_AES_256_GCM_SHA384 (only TLS 1.3)
      - TLS_CHACHA20_POLY1305_SHA256 (only TLS 1.3)
      - TLS_AES_128_GCM_SHA256 (only TLS 1.3)
      - TLS_AES_128_CCM_SHA256 (only TLS 1.3)
      - TLS_AES_128_CCM_8_SHA256 (only TLS 1.3)

      * only if available in OpenSSL, which is not the case in any OpenSSL
        version up to OpenSSL 3.3.x

    - BCP 195 TLS Profile (retired)
      This profile proposes the following set of ciphersuites:
      - TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)
      - TLS_RSA_WITH_AES_128_CBC_SHA (TLS 1.0 - 1.2)
      - TLS_RSA_WITH_3DES_EDE_CBC_SHA (TLS 1.0 - 1.2)

      The first four ciphersuites are modern, state-of the art ciphersuites
      but only work with TLS version 1.2 (or newer). The other two ciphersuites
      offer backward compatibility with older applications implementing the
      AES TLS Secure Transport Connection Profile or the Basic TLS Secure
      Transport Connection Profile (e.g. DCMTK versions older than 3.6.4) and
      can be used with TLS version 1.0 (or newer).

      This profile will support TLS 1.3 when compiled against OpenSSL 1.1.1
      or newer. In this case, the following TLS 1.3 ciphersuites will be
      proposed additionally:

      - TLS_AES_256_GCM_SHA384 (only TLS 1.3)
      - TLS_CHACHA20_POLY1305_SHA256 (only TLS 1.3)
      - TLS_AES_128_GCM_SHA256 (only TLS 1.3)
      - TLS_AES_128_CCM_SHA256 (only TLS 1.3)
      - TLS_AES_128_CCM_8_SHA256 (only TLS 1.3)

    - Non-downgrading BCP 195 TLS Profile (retired)
      This profile proposes the following set of ciphersuites:
      - TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)

      Furthermore, when this profile is active, only TLS version 1.2
      or newer will be negotiated.

      This profile will support TLS 1.3 when compiled against OpenSSL 1.1.1
      or newer. In this case, the following TLS 1.3 ciphersuites will be
      proposed additionally:

      - TLS_AES_256_GCM_SHA384 (only TLS 1.3)
      - TLS_CHACHA20_POLY1305_SHA256 (only TLS 1.3)
      - TLS_AES_128_GCM_SHA256 (only TLS 1.3)
      - TLS_AES_128_CCM_SHA256 (only TLS 1.3)
      - TLS_AES_128_CCM_8_SHA256 (only TLS 1.3)

    - Extended BCP 195 TLS Profile (retired)
      This profile proposes the following set of ciphersuites:
      - TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)
      - TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)
      - TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 (only TLS 1.2)
      - TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (only TLS 1.2)

      Furthermore, when this profile is active, only TLS version 1.2
      will be negotiated. In particular, TLS 1.3 will be disabled.

    - Basic TLS Secure Transport Connection Profile (retired)
      This profile only proposes a single ciphersuite for use
      with TLS 1.0 or newer:
      - TLS_RSA_WITH_3DES_EDE_CBC_SHA

      When this profile is active, only TLS versions up to 1.2
      will be negotiated. TLS 1.3 will be disabled.

    - AES TLS Secure Transport Connection Profile (retired)
      This profile proposes the following set of ciphersuites
      for use with TLS 1.0 or newer:
      - TLS_RSA_WITH_AES_128_CBC_SHA
      - TLS_RSA_WITH_3DES_EDE_CBC_SHA

      When this profile is active, only TLS versions up to 1.2
      will be negotiated. TLS 1.3 will be disabled.

    - Authenticated unencrypted communication (retired)
      This profile proposes a single ciphersuite that offers peer
      authentication and integrity protection, but no encryption.
      This profile should only be used in secure network environments.
      This profile was defined in older versions of the IHE ATNA
      (Audit Trail and Node Authentication) integration profile,
      but has been retired.

      When this profile is active, only TLS versions up to 1.2
      will be negotiated. TLS 1.3 will be disabled.

    Furthermore, on API level it is also possible to start without
    a profile and directly define the set of supported ciphersuites,
    but for security reasons this option has not been made available
    in the command line tools.

    The list of ciphersuites defined by a profile can be extended by
    addition additional profiles from the list of supported ciphersuites
    (see below). The only exception is the unencrypted ciphersuite
    TLS_RSA_WITH_NULL_SHA: For security reasons, this ciphersuite cannot be
    added to one of the secure profiles other than "Authenticated
    unencrypted communication".

    The list of ciphersuites known to DCMTK is shown at the end
    of this document. The list of ciphersuites that is actually supported
    may also depend on the OpenSSL library with which DCMTK is compiled:

    - The CHACHA20 ciphers are only supported starting from OpenSSL 1.1.0

    - The 3DES cipher (TLS_RSA_WITH_3DES_EDE_CBC_SHA) is not available
      in OpenSSL 1.1.0 or newer, unless OpenSSL has been configured
      with "Configure enable-weak-ssl-ciphers <os/compiler>".
      In cases where 3DES is not available, the Basic TLS Secure Transport
      Connection Profile cannot be used and the AES TLS Secure Transport
      Connection Profile will not offer backwards compatibility with the
      Basic TLS profile.

    - The TLS 1.3 ciphersuites are only available when compiled against
      OpenSSL 1.1.1 or newer.

    OpenSSL versions older than 1.0.2 are not supported anymore, and
    we recommend the use of OpenSSL 1.1.1 or newer since because the
    considerably improved TLS 1.3 protocol is only available starting
    with this release.

    ==============================
    NOTES ON CIPHERSUITE SELECTION
    ==============================

    1. Unencrypted Ciphersuites

      TLS defines several "unencrypted" ciphersuites, of which only
      TLS_RSA_WITH_NULL_SHA is also supported by DCMTK.
      This ciphersuite does not provide any confidentiality during data
      transmission - all data is transferred in unencrypted plain text
      and can be read by any man-in-the-middle. It does, however, provide
      peer entity authentication and integrity: it prevents
      any unauthorized modification of data during transfer and
      identifies the communicating entities.  The use of this ciphersuite
      MUST be avoided if confidential (e.g. patient) data is transmitted
      over public networks.

    2. Anonymous Ciphersuites

      TLS defines a number of ciphersuites which use anonymous Diffie-Hellman
      key exchange without signatures. These ciphersuites can be identified by a
      name starting with "TLS_DH_anon_".  They do not permit an authentication
      of the communicating entities and, therefore, are susceptible to
      man-in-the-middle attacks. DCMTK does not support these ciphersuites.

    3. Ciphersuites with Key Length Restrictions

      DCMTK only supports TLS ciphersuite with at least 128 bits of security
      for the symmetric block cipher. Such ciphers can currently be considered
      secure (not breakable by "brute force attacks").

      There are two exceptions, however: The unencrypted ciphersuite
      (TLS_RSA_WITH_NULL_SHA, see above), and the Triple-DES ciphersuite
      (TLS_RSA_WITH_3DES_EDE_CBC_SHA), which is only supported for backwards
      compatibility with older implementations only supporting the
      Basic TLS Secure Transport Connection Profile. While Triple-DES
      has 168 bits key length, the effective security is only 112 bits,
      which is below the threshold chosen for other ciphers.
      Users who want to ensure at least 128 bits of security should use
      the Non-downgrading BCP 195 TLS Profile.

    4. Forward Secrecy Ciphersuites

      TLS defines a number of ciphersuites which implement a security feature
      called "forward secrecy", a technique of ensuring that the communicated
      data are only decipherable for a limited time span by the communicating
      parties. After that time the communicating parties typically achieve
      forward secrecy by destroying cryptographic keys. This prevents an
      attacker from coercing the communicating parties into decrypting old
      ciphertext.  The forward secrecy ciphersuites can be identified by
      the name starting with "TLS_DHE_" or "TLS_ECDHE_".

      Forward secrecy makes it harder for attackers to compromise confidential
      information in transit in encrypted form, and so is more secure than the
      use of non-forward secret cipher suites.  However, some national
      legislations prohibit the use of forward secrecy in terms of non
      recoverable encryption.

      In general, forward secrecy ciphersuites should be preferred.

    ===================================
    TLS Ciphersuites Supported by DCMTK
    ===================================

    The following list shows all TLS ciphersuites currently supported by DCMTK.
    The list of ciphersuites actually available in a DCMTK-based application
    may be smaller depending on the version of OpenSSL used and the way
    OpenSSL has been compiled (see above for details).

      - TLS_RSA_WITH_NULL_SHA
      - TLS_RSA_WITH_3DES_EDE_CBC_SHA
      - TLS_RSA_WITH_AES_128_CBC_SHA
      - TLS_RSA_WITH_CAMELLIA_128_CBC_SHA
      - TLS_RSA_WITH_AES_128_CBC_SHA256
      - TLS_RSA_WITH_AES_128_GCM_SHA256
      - TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA
      - TLS_ECDH_RSA_WITH_AES_128_CBC_SHA
      - TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256
      - TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256
      - TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256
      - TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256
      - TLS_RSA_WITH_CAMELLIA_256_CBC_SHA
      - TLS_RSA_WITH_AES_256_CBC_SHA
      - TLS_RSA_WITH_AES_256_CBC_SHA256
      - TLS_RSA_WITH_AES_256_GCM_SHA384
      - TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA
      - TLS_ECDH_RSA_WITH_AES_256_CBC_SHA
      - TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384
      - TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384
      - TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384
      - TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384
      - TLS_DHE_DSS_WITH_AES_128_CBC_SHA
      - TLS_DHE_DSS_WITH_CAMELLIA_128_CBC_SHA
      - TLS_DHE_RSA_WITH_AES_128_CBC_SHA
      - TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
      - TLS_DHE_DSS_WITH_AES_128_CBC_SHA256
      - TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
      - TLS_DHE_DSS_WITH_AES_128_GCM_SHA256
      - TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
      - TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
      - TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
      - TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
      - TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
      - TLS_ECDHE_ECDSA_WITH_AES_128_CCM
      - TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8
      - TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
      - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
      - TLS_DHE_DSS_WITH_AES_256_CBC_SHA
      - TLS_DHE_RSA_WITH_AES_256_CBC_SHA
      - TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256
      - TLS_DHE_DSS_WITH_AES_256_CBC_SHA256
      - TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
      - TLS_DHE_DSS_WITH_AES_256_GCM_SHA384
      - TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
      - TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
      - TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
      - TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
      - TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
      - TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
      - TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
      - TLS_ECDHE_ECDSA_WITH_AES_256_CCM
      - TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8
      - TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
      - TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384

    TLS 1.3 ciphersuites:

      - TLS_AES_128_CCM_SHA256
      - TLS_AES_128_CCM_8_SHA256
      - TLS_AES_128_GCM_SHA256
      - TLS_CHACHA20_POLY1305_SHA256
      - TLS_AES_256_GCM_SHA384

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