var crypto/elliptic.mask
2 uses
	crypto/elliptic (current package)
		elliptic.go#L68: var mask = []byte{0xff, 0x1, 0x3, 0x7, 0xf, 0x1f, 0x3f, 0x7f}
		elliptic.go#L88: 		priv[0] &= mask[bitSize%8]
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