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# StreamSocketSecurityLevel

`NSStream` defines these string constants for specifying the secure-socket layer (SSL) security level.

```
struct StreamSocketSecurityLevel
```

## Discussion

You access and set these values using the `NSStreamSocketSecurityLevelKey` property key.

## Topics

### Type Properties

[`negotiatedSSL`](/documentation/Foundation/StreamSocketSecurityLevel/negotiatedSSL)

Specifies that the highest level security protocol that can be negotiated be set as the security protocol for a socket stream.

[`none`](/documentation/Foundation/StreamSocketSecurityLevel/none)

Specifies that no security level be set for a socket stream.

[`ssLv2`](/documentation/Foundation/StreamSocketSecurityLevel/ssLv2)

Specifies that SSL version 2 be set as the security protocol for a socket stream.

[`ssLv3`](/documentation/Foundation/StreamSocketSecurityLevel/ssLv3)

Specifies that SSL version 3 be set as the security protocol for a socket stream.

[`tlSv1`](/documentation/Foundation/StreamSocketSecurityLevel/tlSv1)

Specifies that TLS version 1 be set as the security protocol for a socket stream.


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