Is there a standard format for compact 56-bit DES keys? DES keys are traditionally stored as 8-byte blobs, with only the high 7 bits of each byte being meaningful to the algorithm; the low bit of each byte is set so that the population count of the byte is odd.  This makes DES have a key size of 56 bits, rather than 64 bits.

Is there a standard format for storing a 56-bit representation of a DES key?  I was going to store them that way because it means random keys have all their bits used.

For now, I'm just concatenating the 7 bit chunks together, left to right (big-endian sense).

This is for interfacing with a legacy system that uses 3DES; thus, the parity-less format would have 168 bits = 21 bytes.
The one time I've seen a system compress a DES key into 7 bytes, it did it by logically placing the 8 bytes of the standard DES key into an 8x8 table, and then flipping the table along the diagonal axis, so that bit x of byte y of the standard DES key was mapped to bit 7-y of byte 7-x of the compressed key. For example, the first byte of the compressed key consisted of the msbits of all 8 bytes, and the second byte of the compressed key consisted of bit 6 of all 8 bytes, etc.  This moved all the lsbits of each byte into the last byte, which was discarded.

However, I don't believe this was, in any way, standard; it just happened to be what the system I saw did.  This particular transform does have the advantage that the same routine can convert both directions between the standard DES format and the compressed format (that has all the ignored bits in the last byte).