# SecKeyEncrypt(_:_:_:_:_:_:) Encrypts a block of plaintext. ``` func SecKeyEncrypt(_ key: SecKey, _ padding: SecPadding, _ plainText: UnsafePointer, _ plainTextLen: Int, _ cipherText: UnsafeMutablePointer, _ cipherTextLen: UnsafeMutablePointer) -> OSStatus ``` ## Parameters `key` Public key with which to encrypt the data. `padding` The type of padding to use. Possible values are listed in [`SecPadding`](/documentation/Security/SecPadding). Typically, [`PKCS1`](/documentation/Security/SecPadding/PKCS1) is used, which adds PKCS1 padding before encryption. If you specify [`kSecPaddingNone`](/documentation/Security/SecPadding/kSecPaddingNone), the data is encrypted as-is. `plainText` The data to encrypt. `plainTextLen` Length in bytes of the data in the `plainText` buffer. This must be less than or equal to the value returned by the [`SecKeyGetBlockSize(_:)`](/documentation/Security/SecKeyGetBlockSize(_:)) function. When PKCS1 padding is performed, the maximum length of data that can be encrypted is 11 bytes less than the value returned by the [`SecKeyGetBlockSize(_:)`](/documentation/Security/SecKeyGetBlockSize(_:)) function (`secKeyGetBlockSize() - 11`). `cipherText` On return, the encrypted text. `cipherTextLen` On entry, the size of the buffer provided in the `cipherText` parameter. On return, the amount of data actually placed in the buffer. ## Return Value A result code. See [Security Framework Result Codes](/documentation/Security/security-framework-result-codes). ## Discussion The input buffer (`plainText`) can be the same as the output buffer (`cipherText`) to reduce the amount of memory used by the function. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)