A method of authenticating a consumable or detachable element of a continuous inkjet printer comprising: the controller of the printer generating a 1.sup.st item of random information that is dispatched to an authentication circuit of the element; encrypting the 1.sup.st item of information by the authentication circuit using a 1.sup.st encryption algorithm and a 1.sup.st secret key to form a 1.sup.st item of encrypted random information; dispatching the 1.sup.st item of information to the controller; encrypting the 1.sup.st item of information by the controller using a 2.sup.nd encryption algorithm and a 2.sup.nd secret key to form a 2.sup.nd item of encrypted random information; comparing the 1.sup.st item of encrypted random information with the 2.sup.nd encrypted item of random information to authenticate the consumable element; and if the consumable element is authenticated, dispatching at least one part of a 3.sup.rd key, termed the shared key, by the element to the printer.

A post-processing apparatus of an embodiment discharges a sheet determined that writing of information to a wireless tag provided in the sheet is successful to a first paper discharge portion, and discharges a sheet determined that writing of information to a wireless tag provided in the sheet fails to a second paper discharge portion different from the first paper discharge portion.

In an image forming apparatus, a recognition tag is an electronic tag in which recognition information is recorded in advance. A displacement mechanism holds a displacement portion at a first position so as to make a communication access from a tag reader to a recognition tag possible in a case where a replenishment unit is not attached to a unit attachment portion, and holds the displacement portion at a second position so as to make the communication access from the tag reader to the recognition tag impossible in a case where the replenishment unit is attached to the unit attachment portion. The state determining portion determines a state from among a unit attachment state, a unit non-attachment state, and an exceptional state based on information obtained via the tag reader.

A printing system having an IC tag processing function includes a first medium conveyance section and a second medium conveyance section that convey a medium including a plurality of medium sheets each having an IC tag, an IC tag processor that performs reading and writing processing for the IC tag, a printing section that performs printing on the medium, a slack generator that permits generation of slack of the medium, a calculator that calculates a substantial conveyance speed of the medium by the first medium conveyance section, on a basis of a length of a single medium sheet having the IC tag and time needed by the IC tag processor to process the IC tag of the single medium sheet, and a speed determinator that sets a conveyance speed of the medium by the second medium conveyance section to a speed slower than the substantial conveyance speed.

An image forming apparatus includes a communication portion arranged inside a cover covering an image forming portion in the main body of the apparatus and including an antenna surface for use in establishing near field communication. The cover includes a stacking portion in its upper section. The stacking portion is configured to receive a recording medium with an image thereon, the recording medium being discharged outside the main body of the apparatus. The antenna surface faces a region of the upper section of the cover downstream in a direction of discharging the recording medium. The antenna surface at least partially faces a region of the upper section of the cover outside the stacking portion in a direction perpendicular to the direction of discharging the recording medium. The communication portion is capable of communicating with another communication portion using near field communication.

A developer case (10) according to the present invention includes a case main body (30) and an RF tag (36, 37). The case main body (30) contains developer and is attached to an apparatus main body (2, 71) which includes a communication device (14). The RF tag (36, 37) is arranged at the case main body (30) and makes wireless communication with the communication device (14) within a communicable area (A1, A2) around the communication device (14). The case main body (30) includes a plurality of attachment parts (41a, 41b) opposed to the communication device (14) in a state where the case main body (30) is attached to the apparatus main body (2, 71). The RF tag (36, 37) is arranged at one of the plurality of attachment parts (41a, 41b) according to the communicable area (A1, A2) unique to the RF tag (36, 37).

An image forming apparatus includes an image forming unit, a first reader/writer device, a second reader/writer device, and a control unit. The first reader/writer device executes a wireless read/write operation on a wireless tag and is positioned in a sheet conveying path upstream of the image forming unit. The second reader/writer device executes a wireless read/write operation on a wireless tag and is positioned in the sheet conveying path downstream of the image forming unit. The control unit controls the image forming unit, the first reader/writer device, and the second reader/writer device. The control unit controls the second reader/writer device to perform an operation to detect a defect in a wireless tag that is included in a sheet as the sheet is conveyed along the sheet conveying path past the location of the second reader/writer device.

A method of authenticating a consumable or detachable element of a continuous inkjet printer, (CIJ), comprising: the controller of the printer generating and dispatching a 1.sup.st item of random information to an authentication circuit of the element; encrypting the 1.sup.st item of random information by the authentication circuit using a 1.sup.st encryption algorithm and a 1.sup.st secret key to form a 1.sup.st item of encrypted random information; dispatching the 1.sup.st item of encrypted random information to the controller; encrypting the 1.sup.st item of random information by the controller using a 2.sup.nd encryption algorithm and a 2.sup.nd secret key to form a 2.sup.nd item of encrypted random information; and comparing the 1.sup.st item of encrypted random information with the 2.sup.nd encrypted item of random information. If the consumable element is authenticated, a shared key part of a 3.sup.rd key is dispatched by the consumable or detachable element to the CIJ.

A post-processing apparatus of an embodiment discharges a sheet determined that writing of information to a wireless tag provided in the sheet is successful to a first paper discharge portion, and discharges a sheet determined that writing of information to a wireless tag provided in the sheet fails to a second paper discharge portion different from the first paper discharge portion.

A post-processing apparatus of an embodiment discharges a sheet determined that writing of information to a wireless tag provided in the sheet is successful to a first paper discharge portion, and discharges a sheet determined that writing of information to a wireless tag provided in the sheet fails to a second paper discharge portion different from the first paper discharge portion.