# Ciphers

With curl's options
[`CURLOPT_SSL_CIPHER_LIST`](https://curl.se/libcurl/c/CURLOPT_SSL_CIPHER_LIST.html)
and
[`--ciphers`](https://curl.se/docs/manpage.html#--ciphers)
users can control which ciphers to consider when negotiating TLS connections.

TLS 1.3 ciphers are supported since curl 7.61 for OpenSSL 1.1.1+, and since
curl 7.85 for Schannel with options
[`CURLOPT_TLS13_CIPHERS`](https://curl.se/libcurl/c/CURLOPT_TLS13_CIPHERS.html)
and
[`--tls13-ciphers`](https://curl.se/docs/manpage.html#--tls13-ciphers)
. If you are using a different SSL backend you can try setting TLS 1.3 cipher
suites by using the respective regular cipher option.

The names of the known ciphers differ depending on which TLS backend that
libcurl was built to use. This is an attempt to list known cipher names.

## OpenSSL

(based on [OpenSSL docs](https://www.openssl.org/docs/manmaster/man1/openssl-ciphers.html))

When specifying multiple cipher names, separate them with colon (`:`).

### SSL3 cipher suites

`NULL-MD5`
`NULL-SHA`
`RC4-MD5`
`RC4-SHA`
`IDEA-CBC-SHA`
`DES-CBC3-SHA`
`DH-DSS-DES-CBC3-SHA`
`DH-RSA-DES-CBC3-SHA`
`DHE-DSS-DES-CBC3-SHA`
`DHE-RSA-DES-CBC3-SHA`
`ADH-RC4-MD5`
`ADH-DES-CBC3-SHA`

### TLS v1.0 cipher suites

`NULL-MD5`
`NULL-SHA`
`RC4-MD5`
`RC4-SHA`
`IDEA-CBC-SHA`
`DES-CBC3-SHA`
`DHE-DSS-DES-CBC3-SHA`
`DHE-RSA-DES-CBC3-SHA`
`ADH-RC4-MD5`
`ADH-DES-CBC3-SHA`

### AES cipher suites from RFC 3268, extending TLS v1.0

`AES128-SHA`
`AES256-SHA`
`DH-DSS-AES128-SHA`
`DH-DSS-AES256-SHA`
`DH-RSA-AES128-SHA`
`DH-RSA-AES256-SHA`
`DHE-DSS-AES128-SHA`
`DHE-DSS-AES256-SHA`
`DHE-RSA-AES128-SHA`
`DHE-RSA-AES256-SHA`
`ADH-AES128-SHA`
`ADH-AES256-SHA`

### SEED cipher suites from RFC 4162, extending TLS v1.0

`SEED-SHA`
`DH-DSS-SEED-SHA`
`DH-RSA-SEED-SHA`
`DHE-DSS-SEED-SHA`
`DHE-RSA-SEED-SHA`
`ADH-SEED-SHA`

### GOST cipher suites, extending TLS v1.0

`GOST94-GOST89-GOST89`
`GOST2001-GOST89-GOST89`
`GOST94-NULL-GOST94`
`GOST2001-NULL-GOST94`

### Elliptic curve cipher suites

`ECDHE-RSA-NULL-SHA`
`ECDHE-RSA-RC4-SHA`
`ECDHE-RSA-DES-CBC3-SHA`
`ECDHE-RSA-AES128-SHA`
`ECDHE-RSA-AES256-SHA`
`ECDHE-ECDSA-NULL-SHA`
`ECDHE-ECDSA-RC4-SHA`
`ECDHE-ECDSA-DES-CBC3-SHA`
`ECDHE-ECDSA-AES128-SHA`
`ECDHE-ECDSA-AES256-SHA`
`AECDH-NULL-SHA`
`AECDH-RC4-SHA`
`AECDH-DES-CBC3-SHA`
`AECDH-AES128-SHA`
`AECDH-AES256-SHA`

### TLS v1.2 cipher suites

`NULL-SHA256`
`AES128-SHA256`
`AES256-SHA256`
`AES128-GCM-SHA256`
`AES256-GCM-SHA384`
`DH-RSA-AES128-SHA256`
`DH-RSA-AES256-SHA256`
`DH-RSA-AES128-GCM-SHA256`
`DH-RSA-AES256-GCM-SHA384`
`DH-DSS-AES128-SHA256`
`DH-DSS-AES256-SHA256`
`DH-DSS-AES128-GCM-SHA256`
`DH-DSS-AES256-GCM-SHA384`
`DHE-RSA-AES128-SHA256`
`DHE-RSA-AES256-SHA256`
`DHE-RSA-AES128-GCM-SHA256`
`DHE-RSA-AES256-GCM-SHA384`
`DHE-DSS-AES128-SHA256`
`DHE-DSS-AES256-SHA256`
`DHE-DSS-AES128-GCM-SHA256`
`DHE-DSS-AES256-GCM-SHA384`
`ECDHE-RSA-AES128-SHA256`
`ECDHE-RSA-AES256-SHA384`
`ECDHE-RSA-AES128-GCM-SHA256`
`ECDHE-RSA-AES256-GCM-SHA384`
`ECDHE-ECDSA-AES128-SHA256`
`ECDHE-ECDSA-AES256-SHA384`
`ECDHE-ECDSA-AES128-GCM-SHA256`
`ECDHE-ECDSA-AES256-GCM-SHA384`
`ADH-AES128-SHA256`
`ADH-AES256-SHA256`
`ADH-AES128-GCM-SHA256`
`ADH-AES256-GCM-SHA384`
`AES128-CCM`
`AES256-CCM`
`DHE-RSA-AES128-CCM`
`DHE-RSA-AES256-CCM`
`AES128-CCM8`
`AES256-CCM8`
`DHE-RSA-AES128-CCM8`
`DHE-RSA-AES256-CCM8`
`ECDHE-ECDSA-AES128-CCM`
`ECDHE-ECDSA-AES256-CCM`
`ECDHE-ECDSA-AES128-CCM8`
`ECDHE-ECDSA-AES256-CCM8`

### Camellia HMAC-Based cipher suites from RFC 6367, extending TLS v1.2

`ECDHE-ECDSA-CAMELLIA128-SHA256`
`ECDHE-ECDSA-CAMELLIA256-SHA384`
`ECDHE-RSA-CAMELLIA128-SHA256`
`ECDHE-RSA-CAMELLIA256-SHA384`

### TLS 1.3 cipher suites

(Note these ciphers are set with `CURLOPT_TLS13_CIPHERS` and `--tls13-ciphers`)

`TLS_AES_256_GCM_SHA384`
`TLS_CHACHA20_POLY1305_SHA256`
`TLS_AES_128_GCM_SHA256`
`TLS_AES_128_CCM_8_SHA256`
`TLS_AES_128_CCM_SHA256`

## WolfSSL

`RC4-SHA`,
`RC4-MD5`,
`DES-CBC3-SHA`,
`AES128-SHA`,
`AES256-SHA`,
`NULL-SHA`,
`NULL-SHA256`,
`DHE-RSA-AES128-SHA`,
`DHE-RSA-AES256-SHA`,
`DHE-PSK-AES256-GCM-SHA384`,
`DHE-PSK-AES128-GCM-SHA256`,
`PSK-AES256-GCM-SHA384`,
`PSK-AES128-GCM-SHA256`,
`DHE-PSK-AES256-CBC-SHA384`,
`DHE-PSK-AES128-CBC-SHA256`,
`PSK-AES256-CBC-SHA384`,
`PSK-AES128-CBC-SHA256`,
`PSK-AES128-CBC-SHA`,
`PSK-AES256-CBC-SHA`,
`DHE-PSK-AES128-CCM`,
`DHE-PSK-AES256-CCM`,
`PSK-AES128-CCM`,
`PSK-AES256-CCM`,
`PSK-AES128-CCM-8`,
`PSK-AES256-CCM-8`,
`DHE-PSK-NULL-SHA384`,
`DHE-PSK-NULL-SHA256`,
`PSK-NULL-SHA384`,
`PSK-NULL-SHA256`,
`PSK-NULL-SHA`,
`HC128-MD5`,
`HC128-SHA`,
`HC128-B2B256`,
`AES128-B2B256`,
`AES256-B2B256`,
`RABBIT-SHA`,
`NTRU-RC4-SHA`,
`NTRU-DES-CBC3-SHA`,
`NTRU-AES128-SHA`,
`NTRU-AES256-SHA`,
`AES128-CCM-8`,
`AES256-CCM-8`,
`ECDHE-ECDSA-AES128-CCM`,
`ECDHE-ECDSA-AES128-CCM-8`,
`ECDHE-ECDSA-AES256-CCM-8`,
`ECDHE-RSA-AES128-SHA`,
`ECDHE-RSA-AES256-SHA`,
`ECDHE-ECDSA-AES128-SHA`,
`ECDHE-ECDSA-AES256-SHA`,
`ECDHE-RSA-RC4-SHA`,
`ECDHE-RSA-DES-CBC3-SHA`,
`ECDHE-ECDSA-RC4-SHA`,
`ECDHE-ECDSA-DES-CBC3-SHA`,
`AES128-SHA256`,
`AES256-SHA256`,
`DHE-RSA-AES128-SHA256`,
`DHE-RSA-AES256-SHA256`,
`ECDH-RSA-AES128-SHA`,
`ECDH-RSA-AES256-SHA`,
`ECDH-ECDSA-AES128-SHA`,
`ECDH-ECDSA-AES256-SHA`,
`ECDH-RSA-RC4-SHA`,
`ECDH-RSA-DES-CBC3-SHA`,
`ECDH-ECDSA-RC4-SHA`,
`ECDH-ECDSA-DES-CBC3-SHA`,
`AES128-GCM-SHA256`,
`AES256-GCM-SHA384`,
`DHE-RSA-AES128-GCM-SHA256`,
`DHE-RSA-AES256-GCM-SHA384`,
`ECDHE-RSA-AES128-GCM-SHA256`,
`ECDHE-RSA-AES256-GCM-SHA384`,
`ECDHE-ECDSA-AES128-GCM-SHA256`,
`ECDHE-ECDSA-AES256-GCM-SHA384`,
`ECDH-RSA-AES128-GCM-SHA256`,
`ECDH-RSA-AES256-GCM-SHA384`,
`ECDH-ECDSA-AES128-GCM-SHA256`,
`ECDH-ECDSA-AES256-GCM-SHA384`,
`CAMELLIA128-SHA`,
`DHE-RSA-CAMELLIA128-SHA`,
`CAMELLIA256-SHA`,
`DHE-RSA-CAMELLIA256-SHA`,
`CAMELLIA128-SHA256`,
`DHE-RSA-CAMELLIA128-SHA256`,
`CAMELLIA256-SHA256`,
`DHE-RSA-CAMELLIA256-SHA256`,
`ECDHE-RSA-AES128-SHA256`,
`ECDHE-ECDSA-AES128-SHA256`,
`ECDH-RSA-AES128-SHA256`,
`ECDH-ECDSA-AES128-SHA256`,
`ECDHE-RSA-AES256-SHA384`,
`ECDHE-ECDSA-AES256-SHA384`,
`ECDH-RSA-AES256-SHA384`,
`ECDH-ECDSA-AES256-SHA384`,
`ECDHE-RSA-CHACHA20-POLY1305`,
`ECDHE-ECDSA-CHACHA20-POLY1305`,
`DHE-RSA-CHACHA20-POLY1305`,
`ECDHE-RSA-CHACHA20-POLY1305-OLD`,
`ECDHE-ECDSA-CHACHA20-POLY1305-OLD`,
`DHE-RSA-CHACHA20-POLY1305-OLD`,
`ADH-AES128-SHA`,
`QSH`,
`RENEGOTIATION-INFO`,
`IDEA-CBC-SHA`,
`ECDHE-ECDSA-NULL-SHA`,
`ECDHE-PSK-NULL-SHA256`,
`ECDHE-PSK-AES128-CBC-SHA256`,
`PSK-CHACHA20-POLY1305`,
`ECDHE-PSK-CHACHA20-POLY1305`,
`DHE-PSK-CHACHA20-POLY1305`,
`EDH-RSA-DES-CBC3-SHA`,

## Schannel

Schannel allows the enabling and disabling of encryption algorithms, but not
specific cipher suites, prior to TLS 1.3. The algorithms are
[defined](https://docs.microsoft.com/windows/desktop/SecCrypto/alg-id) by
Microsoft.

The algorithms below are for TLS 1.2 and earlier. TLS 1.3 is covered in the
next section.

There is also the case that the selected algorithm is not supported by the
protocol or does not match the ciphers offered by the server during the SSL
negotiation. In this case curl returns error
`CURLE_SSL_CONNECT_ERROR (35) SEC_E_ALGORITHM_MISMATCH`
and the request fails.

`CALG_MD2`,
`CALG_MD4`,
`CALG_MD5`,
`CALG_SHA`,
`CALG_SHA1`,
`CALG_MAC`,
`CALG_RSA_SIGN`,
`CALG_DSS_SIGN`,
`CALG_NO_SIGN`,
`CALG_RSA_KEYX`,
`CALG_DES`,
`CALG_3DES_112`,
`CALG_3DES`,
`CALG_DESX`,
`CALG_RC2`,
`CALG_RC4`,
`CALG_SEAL`,
`CALG_DH_SF`,
`CALG_DH_EPHEM`,
`CALG_AGREEDKEY_ANY`,
`CALG_HUGHES_MD5`,
`CALG_SKIPJACK`,
`CALG_TEK`,
`CALG_CYLINK_MEK`,
`CALG_SSL3_SHAMD5`,
`CALG_SSL3_MASTER`,
`CALG_SCHANNEL_MASTER_HASH`,
`CALG_SCHANNEL_MAC_KEY`,
`CALG_SCHANNEL_ENC_KEY`,
`CALG_PCT1_MASTER`,
`CALG_SSL2_MASTER`,
`CALG_TLS1_MASTER`,
`CALG_RC5`,
`CALG_HMAC`,
`CALG_TLS1PRF`,
`CALG_HASH_REPLACE_OWF`,
`CALG_AES_128`,
`CALG_AES_192`,
`CALG_AES_256`,
`CALG_AES`,
`CALG_SHA_256`,
`CALG_SHA_384`,
`CALG_SHA_512`,
`CALG_ECDH`,
`CALG_ECMQV`,
`CALG_ECDSA`,
`CALG_ECDH_EPHEM`,

As of curl 7.77.0, you can also pass `SCH_USE_STRONG_CRYPTO` as a cipher name
to [constrain the set of available ciphers as specified in the Schannel
documentation](https://docs.microsoft.com/en-us/windows/win32/secauthn/tls-cipher-suites-in-windows-server-2022).
Note that the supported ciphers in this case follow the OS version, so if you
are running an outdated OS you might still be supporting weak ciphers.

### TLS 1.3 cipher suites

You can set TLS 1.3 ciphers for Schannel by using `CURLOPT_TLS13_CIPHERS` or
`--tls13-ciphers` with the names below.

If TLS 1.3 cipher suites are set then libcurl adds or restricts Schannel TLS
1.3 algorithms automatically. Essentially, libcurl is emulating support for
individual TLS 1.3 cipher suites since Schannel does not support it directly.

`TLS_AES_256_GCM_SHA384`
`TLS_AES_128_GCM_SHA256`
`TLS_CHACHA20_POLY1305_SHA256`
`TLS_AES_128_CCM_8_SHA256`
`TLS_AES_128_CCM_SHA256`

Note if you set TLS 1.3 ciphers without also setting the minimum TLS version
to 1.3 then it is possible Schannel may negotiate an earlier TLS version and
cipher suite if your libcurl and OS settings allow it. You can set the minimum
TLS version by using `CURLOPT_SSLVERSION` or `--tlsv1.3`.

## BearSSL

BearSSL ciphers can be specified by either the OpenSSL name (`ECDHE-RSA-AES128-GCM-SHA256`) or the IANA name (`TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256`).

Since BearSSL 0.1:

`DES-CBC3-SHA`
`AES128-SHA`
`AES256-SHA`
`AES128-SHA256`
`AES256-SHA256`
`AES128-GCM-SHA256`
`AES256-GCM-SHA384`
`ECDH-ECDSA-DES-CBC3-SHA`
`ECDH-ECDSA-AES128-SHA`
`ECDH-ECDSA-AES256-SHA`
`ECDHE-ECDSA-DES-CBC3-SHA`
`ECDHE-ECDSA-AES128-SHA`
`ECDHE-ECDSA-AES256-SHA`
`ECDH-RSA-DES-CBC3-SHA`
`ECDH-RSA-AES128-SHA`
`ECDH-RSA-AES256-SHA`
`ECDHE-RSA-DES-CBC3-SHA`
`ECDHE-RSA-AES128-SHA`
`ECDHE-RSA-AES256-SHA`
`ECDHE-ECDSA-AES128-SHA256`
`ECDHE-ECDSA-AES256-SHA384`
`ECDH-ECDSA-AES128-SHA256`
`ECDH-ECDSA-AES256-SHA384`
`ECDHE-RSA-AES128-SHA256`
`ECDHE-RSA-AES256-SHA384`
`ECDH-RSA-AES128-SHA256`
`ECDH-RSA-AES256-SHA384`
`ECDHE-ECDSA-AES128-GCM-SHA256`
`ECDHE-ECDSA-AES256-GCM-SHA384`
`ECDH-ECDSA-AES128-GCM-SHA256`
`ECDH-ECDSA-AES256-GCM-SHA384`
`ECDHE-RSA-AES128-GCM-SHA256`
`ECDHE-RSA-AES256-GCM-SHA384`
`ECDH-RSA-AES128-GCM-SHA256`
`ECDH-RSA-AES256-GCM-SHA384`

Since BearSSL 0.2:

`ECDHE-RSA-CHACHA20-POLY1305`
`ECDHE-ECDSA-CHACHA20-POLY1305`

Since BearSSL 0.6:

`AES128-CCM`
`AES256-CCM`
`AES128-CCM8`
`AES256-CCM8`
`ECDHE-ECDSA-AES128-CCM`
`ECDHE-ECDSA-AES256-CCM`
`ECDHE-ECDSA-AES128-CCM8`
`ECDHE-ECDSA-AES256-CCM8`