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padding: ISO/IEC 9797 method 2
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Sun Yimin
GitHub
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commit
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49
padding/iso9797_m2.go
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49
padding/iso9797_m2.go
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@ -0,0 +1,49 @@
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package padding
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import (
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"errors"
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"github.com/emmansun/gmsm/internal/alias"
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)
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// Add a single bit with value 1 to the end of the data.
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// Then if necessary add bits with value 0 to the end of the data until the padded data is a multiple of n.
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//
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// https://en.wikipedia.org/wiki/ISO/IEC_9797-1
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// also GB/T 17964-2021 C.2 Padding method 2
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type iso9797M2Padding uint
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func (pad iso9797M2Padding) BlockSize() int {
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return int(pad)
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}
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func (pad iso9797M2Padding) Pad(src []byte) []byte {
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overhead := pad.BlockSize() - len(src)%pad.BlockSize()
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ret, out := alias.SliceForAppend(src, overhead)
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out[0] = 0x80
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for i := 1; i < overhead; i++ {
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out[i] = 0
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}
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return ret
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}
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// Unpad decrypted plaintext, non-constant-time
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func (pad iso9797M2Padding) Unpad(src []byte) ([]byte, error) {
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srcLen := len(src)
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if srcLen == 0 || srcLen%pad.BlockSize() != 0 {
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return nil, errors.New("iso/iec 9797-1 method 2: src length is not multiple of block size")
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}
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padStart := -1
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for i, b := range src[srcLen-pad.BlockSize() : srcLen] {
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if b == 0x80 {
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padStart = i
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} else if b != 0 && padStart >=0 {
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padStart = -1
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}
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}
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if padStart >= 0 {
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return src[:srcLen-pad.BlockSize()+padStart], nil
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}
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return src, nil
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}
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82
padding/iso9797_m2_test.go
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82
padding/iso9797_m2_test.go
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package padding
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import (
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"reflect"
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"testing"
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)
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func Test_iso9797M2Padding_Pad(t *testing.T) {
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iso9797 := NewISO9797M2Padding(16)
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tests := []struct {
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name string
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src []byte
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want []byte
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}{
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{"16 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
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{"15 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 0x80}},
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{"14 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 0x80, 0}},
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{"13 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 0x80, 0, 0}},
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{"12 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 0x80, 0, 0, 0}},
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{"11 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 0x80, 0, 0, 0, 0}},
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{"10 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0x80, 0, 0, 0, 0, 0}},
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{"9 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 0x80, 0, 0, 0, 0, 0, 0}},
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{"8 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 0x80, 0, 0, 0, 0, 0, 0, 0}},
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{"7 bytes", []byte{0, 1, 2, 3, 4, 5, 6}, []byte{0, 1, 2, 3, 4, 5, 6, 0x80, 0, 0, 0, 0, 0, 0, 0, 0}},
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{"6 bytes", []byte{0, 1, 2, 3, 4, 5}, []byte{0, 1, 2, 3, 4, 5, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
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{"5 bytes", []byte{0, 1, 2, 3, 4}, []byte{0, 1, 2, 3, 4, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
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{"4 bytes", []byte{0, 1, 2, 3}, []byte{0, 1, 2, 3, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
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{"3 bytes", []byte{0, 1, 2}, []byte{0, 1, 2, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
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{"2 bytes", []byte{0, 1}, []byte{0, 1, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
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{"1 bytes", []byte{0}, []byte{0, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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if got := iso9797.Pad(tt.src); !reflect.DeepEqual(got, tt.want) {
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t.Errorf("iso9797M2Padding.Pad() = %v, want %v", got, tt.want)
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}
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})
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}
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}
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func Test_iso9797M2Padding_Unpad(t *testing.T) {
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iso9797 := NewISO9797M2Padding(16)
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tests := []struct {
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name string
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want []byte
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src []byte
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wantErr bool
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}{
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{"16 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"15 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 0x80}, false},
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{"14 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 0x80, 0}, false},
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{"13 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 0x80, 0, 0}, false},
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{"12 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 0x80, 0, 0, 0}, false},
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{"11 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 0x80, 0, 0, 0, 0}, false},
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{"10 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0x80, 0, 0, 0, 0, 0}, false},
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{"9 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 0x80, 0, 0, 0, 0, 0, 0}, false},
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{"8 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 0x80, 0, 0, 0, 0, 0, 0, 0}, false},
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{"7 bytes", []byte{0, 1, 2, 3, 4, 5, 6}, []byte{0, 1, 2, 3, 4, 5, 6, 0x80, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"6 bytes", []byte{0, 1, 2, 3, 4, 5}, []byte{0, 1, 2, 3, 4, 5, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"5 bytes", []byte{0, 1, 2, 3, 4}, []byte{0, 1, 2, 3, 4, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"4 bytes", []byte{0, 1, 2, 3}, []byte{0, 1, 2, 3, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"3 bytes", []byte{0, 1, 2}, []byte{0, 1, 2, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"2 bytes", []byte{0, 1}, []byte{0, 1, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"1 bytes", []byte{0}, []byte{0, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"1 bytes with tag", []byte{0x80}, []byte{0x80, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"3 bytes with tag", []byte{0x80, 0, 0x80}, []byte{0x80, 0, 0x80, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"19 bytes with tag", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0x80, 0, 0x80}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0x80, 0, 0x80, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
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{"invalid src length", nil, []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, true},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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got, err := iso9797.Unpad(tt.src)
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if (err != nil) != tt.wantErr {
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t.Errorf("case %v: iso9797M2Padding.Unpad() error = %v, wantErr %v", tt.name, err, tt.wantErr)
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return
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}
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if !reflect.DeepEqual(got, tt.want) {
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t.Errorf("case %v: iso9797M2Padding.Unpad() = %v, want %v", tt.name, got, tt.want)
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}
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})
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}
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}
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@ -21,3 +21,10 @@ func NewANSIX923Padding(blockSize uint) Padding {
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}
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return ansiX923Padding(blockSize)
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}
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func NewISO9797M2Padding(blockSize uint) Padding {
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if blockSize == 0 || blockSize > 255 {
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panic("padding: invalid block size")
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}
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return iso9797M2Padding(blockSize)
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}
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