# 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`

## GSKit

Ciphers are internally defined as [numeric
codes](https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_73/apis/gsk_attribute_set_buffer.htm). libcurl
maps them to the following case-insensitive names.

### SSL2 cipher suites (insecure: disabled by default)

`rc2-md5`
`rc4-md5`
`exp-rc2-md5`
`exp-rc4-md5`
`des-cbc-md5`
`des-cbc3-md5`

### SSL3 cipher suites

`null-md5`
`null-sha`
`rc4-md5`
`rc4-sha`
`exp-rc2-cbc-md5`
`exp-rc4-md5`
`exp-des-cbc-sha`
`des-cbc3-sha`

### TLS v1.0 cipher suites

`null-md5`
`null-sha`
`rc4-md5`
`rc4-sha`
`exp-rc2-cbc-md5`
`exp-rc4-md5`
`exp-des-cbc-sha`
`des-cbc3-sha`
`aes128-sha`
`aes256-sha`

### TLS v1.1 cipher suites

`null-md5`
`null-sha`
`rc4-md5`
`rc4-sha`
`exp-des-cbc-sha`
`des-cbc3-sha`
`aes128-sha`
`aes256-sha`

### TLS v1.2 cipher suites

`null-md5`
`null-sha`
`null-sha256`
`rc4-md5`
`rc4-sha`
`des-cbc3-sha`
`aes128-sha`
`aes256-sha`
`aes128-sha256`
`aes256-sha256`
`aes128-gcm-sha256`
`aes256-gcm-sha384`

## 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. They are
[defined](https://docs.microsoft.com/windows/desktop/SecCrypto/alg-id) by
Microsoft.

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 will return error
`CURLE_SSL_CONNECT_ERROR (35) SEC_E_ALGORITHM_MISMATCH`
and the request will fail.

`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

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

`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`

## 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`