Production Specification

07/03/02

B roa dcom Co rpo rat ion

Document

5802-DS03-405-R

Invalid Encryption/Authentication Operations

This section details scenarios that the software should never request the chip to process. These can cause unknown results

being written to memory, or possibly a chip hang condition.

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Zero-length packets: These can arise in several ways, all of which should be avoided. One way is to have a zero total

packet length in a MCR structure. Another is to have a non-zero packet length, but to set the crypto offset equal to or

greater than the entire length of the packet.

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Zero-length descriptors: All data buffer entries in input and output descriptor chains should have a non-zero length.

Similarly, requesting the chip to use a zero output fragment size from the output fragment register would lead to

unpredictable results.

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Erroneous parameter specifications: Situations such as illegal authentication specifiers, misaligned structure members,

and misaligned output packet payload data, should be guaranteed to never occur.

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Output descriptors that point to misaligned output data buffers: All output data should be aligned on 32-bit boundaries.

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Output descriptors that indicate an output buffer byte length that is not a multiple of four: All output data buffers must

have a length that is multiple of 32-bits.

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Non-zero crypto offset with crypto disabled.

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Packets with both authentication and crypto disabled.

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Packets with crypto disabled, but with an output descriptor chain of length > 1 specified: For packets that have no crypto

output (hence must have an authentication output), there must be one, and exactly one output descriptor specified in

the Master Command Record. Only the next field of this descriptor is used to write out the HMAC codes. Other fields of

this descriptor (in particular the data buffer address and size) are ignored.

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Incorrect packet size for cryptography: Whenever 3DES is enabled, the length of input data to be encrypted must be a

multiple of eight bytes. The input data length is calculated as total packet size minus the number of 32-bit dwords

specified by the crypto offset context field. Giving the chip a crypto data length that is not a multiple of eight bytes could

hang the chip. IPsec padding guarantees that this never happens.

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Crypto offset that leads to a data length for encryption or decryption that is not multiple of 64-bits: For instance, a crypto

offset of one word with a total packet length of 40 words would force the crypto unit to process 39 words, which is not a

multiple of eight bytes. However, a crypto offset of one word with a packet length of 41 words is fine, as is a crypto offset

of two words with a packet length of 40 words.

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Non-zero crypto offset for packets that do not have both crypto and authentication enabled: If authentication is disabled,

the crypto offset must be set to zero. Crypto offset can not be used as a programmable skip length for crypto-only

packets.

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Writing to the MCR register with PCI master mode disabled: Doing so causes the control microcode to start processing

and hang, waiting for a PCI master mode access that never begins.

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The #Packet or #Key Setup in the first field in an MCR cannot be zero.

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The Flags field (second field) in an MCR must be zeroed out before sending the MCR pointer to DMA register on the