These two methods are based on "National Industrial Security Program Operating Manual", NISPOM (also known as US DoD 5220.22-M), of United States Department of Defense from January 1995 (chapter 8, section 3, 8-306. Maintenance).
The first alternative consists of parts E (which is D without verifying), C and E (once more) of the clearing and sanitization matrix.
Pass Matrix Pattern
1 E [1] Random character X
2 E [2] Bit-wise complement of X
3 E [3] Random data
4 C Random character Y
5 E [1] Random character Z
6 E [2] Bit-wise complement of Z
7 E [3] Random data
X, Y, Z = [0,255]
The latter version includes only part E of the matrix, and the first two passes consist of constants instead of random characters.
Pass Matrix Pattern
1 E [1] 00000000, 0x00
2 E [2] 11111111, 0xFF
3 E [3] Random data
All random data is created with the ISAAC pseudorandom number generator.
Even though these overwriting methods are faster than the Gutmann method, they are less secure, especially when there is a chance that someone will try to use hardware recovery methods in attempt to restore the previous data.
These methods are not suitable for erasing data on compressed drives, because some of the passes contain compressible data.
References:
National Industrial Security Program Operating Manual (NISPOM)
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