createDecipheriv(algorithm, key, iv, options): DecipherCCM
Creates and returns a Decipher object that uses the given algorithm, key and initialization vector (iv).
The options argument controls stream behavior and is optional except when a
cipher in CCM or OCB mode (e.g. 'aes-128-ccm') is used. In that case, the authTagLength option is required and specifies the length of the
authentication tag in bytes, see CCM mode. In GCM mode, the authTagLength option is not required but can be used to restrict accepted authentication tags
to those with the specified length.
For chacha20-poly1305, the authTagLength option defaults to 16 bytes.
The algorithm is dependent on OpenSSL, examples are 'aes192', etc. On
recent OpenSSL releases, openssl list -cipher-algorithms will
display the available cipher algorithms.
The key is the raw key used by the algorithm and iv is an initialization vector. Both arguments must be 'utf8' encoded
strings,Buffers, TypedArray, or DataViews. The key may optionally be
a KeyObject of type secret. If the cipher does not need
an initialization vector, iv may be null.
When passing strings for key or iv, please consider caveats when using strings as inputs to cryptographic APIs.
Initialization vectors should be unpredictable and unique; ideally, they will be
cryptographically random. They do not have to be secret: IVs are typically just
added to ciphertext messages unencrypted. It may sound contradictory that
something has to be unpredictable and unique, but does not have to be secret;
remember that an attacker must not be able to predict ahead of time what a given
IV will be.
Creates and returns a
Decipherobject that uses the givenalgorithm,keyand initialization vector (iv).The
optionsargument controls stream behavior and is optional except when a cipher in CCM or OCB mode (e.g.'aes-128-ccm') is used. In that case, theauthTagLengthoption is required and specifies the length of the authentication tag in bytes, seeCCM mode. In GCM mode, theauthTagLengthoption is not required but can be used to restrict accepted authentication tags to those with the specified length. Forchacha20-poly1305, theauthTagLengthoption defaults to 16 bytes.The
algorithmis dependent on OpenSSL, examples are'aes192', etc. On recent OpenSSL releases,openssl list -cipher-algorithmswill display the available cipher algorithms.The
keyis the raw key used by thealgorithmandivis an initialization vector. Both arguments must be'utf8'encoded strings,Buffers,TypedArray, orDataViews. Thekeymay optionally be aKeyObjectof typesecret. If the cipher does not need an initialization vector,ivmay benull.When passing strings for
keyoriv, please considercaveats when using strings as inputs to cryptographic APIs.Initialization vectors should be unpredictable and unique; ideally, they will be cryptographically random. They do not have to be secret: IVs are typically just added to ciphertext messages unencrypted. It may sound contradictory that something has to be unpredictable and unique, but does not have to be secret; remember that an attacker must not be able to predict ahead of time what a given IV will be.